Use a formula if my IF function returns a false?

Good morning,

I've figured out how to use the IF function to turn a cell blank like this if true: =IF(AP13="", "","yes")
I'm trying to do something like this : =IF(AP13="", "","=A1+A2+A3")
Or I could put the =A1+A2+A3 formula in another cell and reference that cell, but I can't figure out how to get it to reference another cell as a returned value either.
Any help here would be great. I doesn't need to be an IF function. I'm just trying to turn the cell (G1) blank if the reference cell (AP13) is blank. If the reference cell (AP13) is not blank then I need my original value, from the original formula (from a separate cell if need be), to fill G1.
All cell references in this post are just for example.

Thanks so much,
Lucas

Wow,

Thank you so much AliGW! If you have time, do you mind explaining how you got that, or why it works? I googled for a good hour and didn't find anything.
That's so quick you'd think that would be included in the little helper box that shows up while filling out a function.

Thanks again,
That was awesome,
Lucas

Oh I see, I thought there was extra set of "" in the formula you gave me so I thought there was a third value after the true/false fill-ins. It's unbelievable how easy this was and that I couldn't find any reference on how to use a formula a formula as the returned value in all the searching I did. So how would I know not to put "" around the A1+A2 formula?

Thanks again,
Lucas