Hi,me again

Last one today since i need to stop digressing and get on with some work

If i have 3 columns and a total box

A = Income
B = Paydate
C = Paid

the total box is outstanding payment total

What i am trying to achieve

Col A values to be totalled in Outstanding payment box if no date is in col B.
once a Date (paydate) is input into B then the outstanding payment be removed from the outstanding total. I have a col C (paid) with a "yes no" drop list but would prefere not to use it if it can be done using the date box.

thanks in advance