When applying payments to families with multiple children, let us toggle between students to click on everything that will be paid for

If one parent is paying for multiple students, they write a check (for instance) for all of their children. So if part of the check is for one child we click on what they are paying for but then we have to keep track of how much is left on the check when we go to the next child to click on what the check is covering, and then again if they have more children after that. It would be easier if we can click on one child, have the system keep track of whats left on their payment as we go to the next child and click boxes until the amount of the check is used up.