I have a formula adding & subtracting the number values in 3 different cells
into a fourth cell, however I need to change the formula so that if one of
the cells is blank, the fourth cell sum will show blank too.

I think a simple IF formula will work, but I don't know how to tell the
formula if the cell is blank.

example: A1 =Sum(A2-A3+A4)

I've tried something like: IF(A2=blank,"",sum(A2-A3+A4)
but I get an error.