Office 2k

Spreadsheet is for our local historical society bank account.
Column c="expenses", e="deposits" and g="running balance". The first g
column(g-3) is a carryover from previous year.

What was done in past was the formula G11-C12+E12, etc.,etc. was in all
cells in column G. Problem was the total was carried all the way down the
sheet which looks bad. One sheet per year with ~ 65 entries. Don't write
that many checks or have many deposits. :)

What I'm trying to do is have the running balance columns blank unless
something is in either expense or deposit column. Then it should add/subract
value from cell above.
Here's example of what I'm trying to do but this formula isn't working
correctly. It's leaving a #VALUE! in the cell.
=IF(C12="",IF(E12-"",G11-C12+E12))

Suggestions please,