=if(B10,A1+B1,A1)

drag fill down the column.

--
Regards,
Tom Ogilvy

"Janna" wrote in message
...
I would like to write a formula in column C that if column B's amount is
positive, to add it to the amount in Column A, but if the amount in
column B
is negative, to simply add zero to the amount in Column A.