OPINION
SULLIVAN, Judge.Appellant, Jerry Ogle, appeals the trial court's judgment finding him delinquent in the payment of previously ordered child support in the sum of $43,960.00. Jerry claims that the trial court erred in finding that, pursuant to a property settlement agreement, he was obligated to pay noneducational child support upon the parties' youngest child attending an institution of higher learning.
We affirm.
On May 22, 1987, the trial court issued an order dissolving Jerry and Margaret Ogle's marriage and adopting the parties' Property Settlement Agreement ("Settlement Agreement"). Pursuant to the Settlement Agreement, Margaret received custody of their two children, Nicholas, then twelve, and Stephanie, then eight, and Jerry agreed to pay $231.00 per week ($115.50 per child) in child support. The Settlement Agreement further provided:
"When either of the minor children are able and elect to attend a college, trade school or other post-secondary educational institution, [Jerry] shall pay the room, board, books, tuition and fees incidental to such education together with such support as the court may from time to time deem proper." Appellant's Appendix at 8.
On February 15, 1990, Margaret filed a petition to modify child support. On April 30, 1990, Jerry and Margaret agreed that Jerry's child support would be increased to $280.00 per week, and the trial court approved this modification.1
Thereafter, Jerry made regular support payments of $280.00 until August 24, 1996, which was Stephanie's eighteenth birthday and the day after she went to Asbury College in Kentucky. Stephanie attended Asbury College for one year, and then attended Anderson University in Anderson, Indiana for three years until she received her degree. While Stephanie attended college, Jerry paid all of Stephanie's expenses pursuant to the Settlement Agreement, including room, board, books, tuition, and other incidental costs associated therewith Jerry, however, did not make any non-educational child support payments, ie. $280.00 per week. At no point after the 1990 modification did Jerry or Margaret attempt to further modify the prior child support order of $280.00 per week.2
On February 15, 2001, Margaret filed a verified motion to show cause alleging Jerry's failure to pay non-educational child support from August 24, 1996 through Au*647gust 24, 1999, and seeking to establish a delinquency.3 On July 12, 2001, Margaret moved to dismiss her verified motion to show cause and filed a motion to reduce support delinquency to judgment. The trial court held a hearing on August 27, 2001. The day after the hearing, the trial court issued an order finding Jerry delinquent in the payment of previously ordered child support in the sum of $43,960.00, or $280.00 per week for the three-year period.
Upon appeal, Jerry argues that the Settlement Agreement did not obligate him to pay non-educational child support when the youngest child, Stephanie, attended an institution of higher learning. In the alternative, Jerry argues that if we conclude that he was obligated to pay such noneducational child support in addition to Stephanie's college expenses, at the very least, he should receive a credit against the arrearage for the time Stephanie was away at school.
We begin by noting that upon dissolution of marriage, parties are free to draft their own settlement agreements. Niccum v. Niccum, 734 N.E.2d 637, 639 (Ind.Ct.App.2000). Such agreements are contractual in nature and become binding upon the parties onee the trial court merges and incorporates such into the divorcee decree. In re Marriage of Loeb, 614 N.E.2d 954, 957 (Ind.Ct.App.19983). This court will enforce an agreement concerning the custody and support of children even though the divorcee court would otherwise not have the authority to do as the parties agreed. Id.; see also Schueneman v. Schueneman, 591 N.E.2d 608 (Ind.Ct. App.1992) (holding that although a parent's general duty to support his or her child ends when the child reaches twenty-one years of age, parents are free to enter into binding agreements to do so). When interpreting such agreements, we apply the general rules applicable to construction of contracts. Niccum, 734 N.E.2d at 639.
The interpretation and construe, tion of contract. provisions is a function for the courts. Id. Upon appeal, we employ the same standard of review as applied by the trial court, that is, unless the terms of the contract are ambiguous, they will be given their plain and ordinary meaning. Id. Where the terms of a contract are clear and unambiguous, the terms are conclusive, and we will not construe the contract or look to extrinsic evidence, but will merely apply the contractual provisions. Id. The terms of a contract are not ambiguous merely because the parties disagree as to the proper interpretation of the terms. Id. '
In their respective briefs, Jerry and Margaret assert that the terms of their Settlement Agreement are unambiguous, but they disagree as to the proper interpretation of the terms regarding-child support. Jerry and Margaret both direct us to the language of the Settlement Agreement. Jerry asserts that the terms of the Settlement Agreement clearly indicate that he and Margaret provided for two separate and distinct support seenarios--child support until the time "the minor children are able and elect to attend a college ...," and child support in the form of educational expenses associated with college when, and if, the minor child so decides.
Jerry argues that the language of the Settlement Agreement should be inter*648preted to mean that "when" Stephanie went off to college, he was obligated to pay only the expenses associated with such higher education "together with such, support as the court may from time to time deem proper." Jerry focuses on the emphasized portions and argues that because the language is "permissive," it clearly indicates that the child support obligation of $280.00 per week terminated once Stephanie went to college, and that he was not obligated to pay non-educational child support unless a subsequent support order was entered.
Our review of that portion of the Settlement Agreement indicates that the provision concerning child support is clear and unambiguous. However, we do not accept Jerry's interpretation as to how it should be construed. The Settlement Agreement does not provide that Jerry's non-educational child support obligation terminated when Stephanie went to college. Giving the terms their plain and ordinary meaning, it is apparent that Jerry was obligated to pay non-educational child support in addition to college expenses "[when either of the minor children [were] able and elected] to attend a college." The language "together with such support as the court may from time to time deem proper" is appropriately construed, not as suggested by Jerry, but as permitting the court to further modify the then current amount of non-educational support if such was later determined to be inappropriate given the cireumstances. We therefore conclude that pursuant to the Settlement Agreement, Jerry was obligated to pay non-educational support in the amount of $280.00 per week from August 24, 1996 through August 24, 1999.
Given that we have concluded that Jerry was obligated to pay non-educational child support in addition to college expenses, we now address Jerry's argument that he is entitled to a credit against his arrearage for the time Stephanie was away at college and he provided support by paying all of her college expenses. -Specifically, Jerry asserts that it would amount to a windfall to pay Margaret the arrearage for expenses she did not incur.
It is a long-standing rule that the non-custodial parent may not unilaterally reduce a child support obligation but must make payments in the manner, amount, and at the times required by an in gross support order until a court orders a modification or all of the children are emancipated or reach the age of twenty-one years. Thacker v. Thacker, 710 N.E.2d 942, 944 (Ind.Ct.App.1999); Nill v. Martin, 686 N.E.2d 116, 117 (Ind.1997); Kirchoff v. Kirchoff, 619 N.E.2d 592, 596 (Ind.Ct.App.1993). An extension of this rule is that any modification of a support obligation may relate back, at the earliest, to the date a petition to modify was filed. Beehler v. Beehler, 693 N.E.2d 638, 641 (Ind.Ct.App.1998). Indeed, a court is without power to retroactively modify an obligor's duty to pay a delinquent child support obligation. Ind.Code § 31-16-16-6 (Burns Code Ed. Repl.1997); Beshlier, 6983 N.E.2d at 640. "[Olnce funds have accrued to a child's benefit under a court order, the court may not annul them in a subsequent proceeding." Martin 686 N.E.2d at 118.
Here, Jerry's argument is essentially a request for us to disregard the Settlement Agreement and retroactively modify his child support obligation. Jerry and Margaret executed a Settlement Agreement wherein they agreed upon the terms of child custody and child support, including a provision which required Jerry to pay college expenses in addition to non-educational child support. Jerry and Margaret subsequently modified the amount of non-educational child support, and it is this *649in gross support order which remained in effect until the court ordered a modification or Stephanie turned twenty-one. At no time, however, did either Jerry or Margaret petition to modify or terminate the then existing child support order. Thus, Jerry was obligated to pay Stephanie's college expenses and make the support payments in the manner, amount, and at the times required by the Settlement Agreement, and as modified by the subsequent agreement. By failing to pay the non-educational support while Stephanie was at college, Jerry unilaterally reduced his support obligation, which he is not permitted to do.
Jerry nonetheless argues that because payment of the entire amount of the ar-rearage would amount to a windfall to Margaret, he is entitled to a credit against his acerued support obligation. However, we find nothing in the eases to which Jerry refers which supports the position that a seeming windfall to the custodial parent permits a court to retroactively modlfy an accrued support obligation.
In Thacker, the court held that the noncustodial parent should be ordered to pay, directly to the son, an arrearage, which accumulated during the period when the son was absent from the custodial parent's home. 710 N.E.2d at 946. The court reasoned that it could not reasonably order the non-custodial parent to pay the custodial parent money for support of the son, when. the custodial parent did not in fact support him. Id. at 945. The court concluded that under the cireumstances, such would amount to a windfall for the custodial parent for expenses she did not actually incur. Id. at 945-46. The court did not, however, retroactively modify or in any way reduce the child support arrearage because of the windfall which would have resulted to the custodial parent.
'In Martin, the court cited three narrow situations in which credit against accrued support obligations is permitted. Jerry asserts that the third exception, which permits a credit in situations where a permanent change of custody has in effect occurred, follows the policy that a custodial parent should not receive child support for periods of time during which the custodial parent is not supporting the child because to do so would result in a windfall to the custodial parent. To some extent this is true. However, this exception is not applicable to the case before us. Here, while Stephanie was away at college, she was still under the care and supervision of Margaret as the custodial parent. Indeed, during vacations and summer. break, except for a two week period when she traveled to England, Stephanie resided with her mother. We cannot say that simply because Jerry paid all of Stephanie's expenses while she was away at college that such, in effect amounts to a permanent change in custody.
Competing with the notion that a custodial parent should not receive a windfall is the freedom of contract. As noted above, onee a court incorporates a settlement agreement devised by the parties into a divorce decree, the terms of that. agreement are binding. Loeb, 614 N.E.2d at 957. As noted, Jerry and Margaret agreed to the terms of the Settlement Agreement, including the provision which required Jerry to pay all college expenses in addition to non-educational child support. While this may seem to result in a windfall for. Margaret, Jerry is bound by the terms of the Settlement Agreement.
We do recognize, however, that pursuant to the Settlement Agreement, Jerry may have been entitled to a partial or full abatement of his non-educational child support obligation for the time Stephanie was at college had he petitioned the court *650for a modification when Stephanie went off to school. The Settlement Agreement contemplated that very thing in that it provided that Jerry would pay for college expenses "together with such support as the court may from time to time deem proper." As we noted, this provision is appropriately interpreted as permitting the court to modify the non-educational support order as cireumstances demanded.
While Jerry's actions of paying all of Stephanie's college expenses are commendable, such does not excuse his failure to pay: non-educational child support in accordance with the Settlement Agreement. Further, Jerry's request for a credit against any arrearage is simply a request for retroactive modification of his support obligation, which we are not permitted to do. Therefore, we conclude that the trial court did not err in finding Jerry to be delinquent in the payment of child support in the sum of $48,960.00.
The judgment of the trial court is affirmed.
DARDEN, J., concurs. BAKER, J., dissents with separate opinion.. Jerry and Margaret agree that the arrangement to increase Jerry's child support obligation to $280.00 per week modified the then existing support order under the Settlement Agreement to an in gross support order. An in gross support order is an order for the obligated party to pay a specified sum of undivided support for more than one child. Isler v. Isler, 422 N.E.2d 416, 419 (Ind.Ct.App.1981).
. We note that Margaret failed to assert her rights until nearly four and one-half years after Jerry stopped paying non-educational child support. Margaret's unwarranted delay has resulted in a substantial judgment against Jerry. Although we do not condone this delay, Jerry failed to present any issue in this regard.
. Margaret concedes that when Stephanie turned 21 on August 24, 1999, the in gross child support order terminated. Thus, we are concerned only with the three-year period from August 24, 1996, when Jerry stopped paying the non-educational child support, through August 24, 1999, when Stephanie turned 21. t_