repeating values

[Peach]

I have this formula to calculate my value balance:
=IF(ISBLANK($C5),$O4-$D5*$L5,$O4+$C5*$L5)

This works but when I copy my formula down the column I get repeating values
for blank cells.

What I want to do is "" is c5 is blank and if it isn't blank I want to do
either of the other formulas.
Can i have two = if to do this?

 

[JLatham]

You're going to need to nest another IF testing one of the other values (or
testing C5 again), as
=IF(ISBLANK($C5),"",IF($C5="SUBTRACT",$O4-$D5*$L5,$O4+$C5*$L5))