Did you try the formula? What answer did you get?
Firstly, look at the Excel Help for the SUM function. If you want to use
the SUM function to add F2 and F3 then you can use SUM(F2,F3) with the
arguments separated by a comma, but alternatively F2+F3 will add F2 and F3
without needing a SUM around it.
Secondly, look at the Excel help for the ROUNDUP function to see the syntax
of that function.
If you are saying that having added F2 and F3 you want to test the total
against zero, and if the total is positive you want to round up to 2 places
of decimals, then you could use
=If(F2+F3>0,Roundup(F2+F3,2),"whatever answer you want if F2+F3 is zero or
negative")
If that isn't what you are trying to do, you may wish to refine your
question.