Update subform field

[Tara]

Please bear with me as I try to explain what I need.

I have a database that is used for tracking employee contributions to a
non-taxable medical reimbursement plan. I currently have frmContributions
which is used to view yearly employee contributions. Form fields are:
EmployeeID, EmployeeName, YearlyContribution. On this form I also have a
subform which will be used to track withdrawls from the account. The subform
fields are EmployeeID, StartAmt, Request, Paid, and Remaining. I need the
first record in this subform to list StartAmt as the YearlyContribution
amount (from the parent form). I need Paid to be calculated so that as long
as the Request is not larger than the StartAmt, the total requested amount is
Paid. If the Request amount is larger than the StartAmt, then the StartAmt
is the actual amount Paid. The field Remaining would then calculated based
on StartAmt - Paid. On top of this, I need the next record to show the
StartAmt as the same amount as Remaining on the previous record.

Any ideas on where to start would be appreciated

 

[Tara]

Update: I've got the first part of this figured out, that is how to get the
fields to update. Except for one little problem. I want the very first
record to show the YearlyContribution as the StartAmt (I've got that
working), but every record thereafter needs to show the previous record's
Remaining amount in the StartAmt field. Right now, it's still defaulting to
the YearlyContribution amount.