Modifications of child support are governed by Sections 452.370 and 452.340 R.S.Mo. A prerequisite to a modification is a change in circumstances so substantial and continuing as to make the terms of the order unreasonable. Our office has been successful in obtaining orders that require ex-spouses to contribute to the payment of college expenses for children. As with child custody, there is no set amount of time that must pass from the time the order was entered or set of facts that must occur before a motion to modify can be filed. We have succeeded in obtaining modifications when our client’s income has changed, if the other party’s income has changed, if a significant amount of time has passed since the current decree was entered, if the cost of day care has changed, and when children are nearing entering college.