One approach would be to have a main table to store the fact that a payment
was made to an employee on a date, and a related table for each line item in
the payment. The 'overtime' would be a separate line item.

tblPay
   PayID    AutoNumber
   PayDate    Date/Time (date of the payment)
   EmployeeID    foreign key to tblEmployee.EmployeeID

tblPayDetail:
   PayID            foreign key to tblPay.PayID
   PayTypeID    lookup values 'Regular', 'Overtime', ...
   Hours            number (Double)
   PayRate       Currency (dollars per hour)
You may also need an EndDate or date range in tblPayDetail, e.g. if you need
to pay ahead for 'Vacation' pay.

Then it is a matter of programmatically looping through all the timesheet
records that have not already been paid, up to the PayDate, creating records
in these 2 tables, and flagging each timesheet entry as paid. This process
would typically need a batch number, so you can undo the last batch, fix the
timesheets, and have another shot at it if necessary.

Your interface should lock the timesheet entries that have already been
'paid' so they can't be modified. If a correction is needed after the pays
have been administered, it should be by way of a reversal in the next pay
rather than allowing edits of the timesheets. (There will be some extra code
to get this right, e.g. if the timesheets recorded that the guy worked 42
hour week and so you paid him 40 hours regular + 2 hours overtime, and then
it was discovered that a timesheet was duplicated and he worked only 37
hours, you need 2 reversal entries: one removing 2 hours overtime, and
another removing 3 hours regular.)

Hope that at least takes you in a useful direction.