Calculate outstanding balance

Hello!, I wonder if anyone could help please.

Imagine a regular Budget type of spreadsheet

Column A we have titles

Column B we have figures, B32 is the Sum of the figures e.g. =Sum(B2:b30)

Column C we have whether the amount has been paid. This shows in a very basic Y or N

At the bottom of Column C, I basically want the reverse of B32, where for each Y the corresponding Number in Column B is taken away from B32 so that i have an outstanding balance.

The formulas ive tried feel like im making this a lot more complicated that i need too!