Numbers IF formula for additions/subtractions on MacBook Pro

There is no "stop" like there is in programming.

This is the exact thing you asked for (other than "stop")

=IFS(AND(F29="",G29=""),"",F29>=0,G29+F29, F29<0, G29-F29)

The result is either a null string "" (which appears as a blank cell) or mathematical result.

However,

if F29>=0 then G29 + F29 else if F29<0 then G29-F29

can be simplified to G29+ABS(F29)

so the simplified answer is

IF(AND(F29="",G29=""),"",G29+ABS(F29))

Note that if F29 or G29 is empty, but the other has a value, the empty cell is treated as a zero. If you meant "if F29 OR G29 is empty then stop", replace the AND with OR.

Your question is too vague to get a direct answer.

IF() can certainly trigger additions and subtractions but you'll need to show more.

A sample screenshot of sample data should be sufficient, with an explanation of what you want the formula to do - for example:

"IF the cell B2 is positive, then add C2 and D2, otherwise subtract D2 from C2"

That's just a simple example and they can get far more complex, but knowing what logic you want to implement is key.

So, what is it you're trying to do?