Amortizing pay outs through payroll

One of my clients have the following requirements - they may agree to pay some their employee certain amount (it is a negotiated amount which varies with each employee), say $3000 as education allowance. They pay this out through payroll. These pay outs may happen periodically (not necessarily every payroll) and the amounts paid out each time need not be the same. Client wants a way of setting up these amounts and keeping track of the pay out and balance.

A similar functionality is available for deduction balance type and amount in PR14. But not so for pay codes. Any suggestions on work arounds or minimizing the complexity of the customizaiton would be appreciated