C=A-B i want my c=a in next row in my report

[Guest]

I am making a report.
A= Cost
B= Amount Paid
C= Balance
In my form My equation is:
C= A-B
When I go to Next record or new record or when I edit my recordI want my
C Becomes = A and then
Balnace should be based on new C to calculate balance.
Please someone help me.
Thanks
Tony

 

[Rick B]

We saw your first post. No need to ask again.