I'd like to create a timesheet for an employee, to keep track of their hours, total pay, and current balance due.  Below is a screenshot with more detail.

I'd like total hours to display all of the results B6:Bxxx.  Total Pay will sum all of the values from C6 and onward.  I'd like the "Pay Due" (C3) to show all of the balance due for those cells that don't have a pay date listed.  With the example above, I'd like it to display "5" but then when a date is entered into the "pay date" column for that row, the Pay Due would be back to 0.  I hope this makes sense, and any thoughts are appreciated!