This is very useful tip to calculate the part formula portion of a long formula.
Suppose you have a long formula and you just wish to know the part formula result to proceed further. In this case you can use the wonder key F9.
Just select the formula portion and press F9 and you will see that the selected formula portion has been converted to output result. To get back the formula, you can press Undo i.e, Ctrl + Z key combination.
Example:- If you have a date in cell A1 as 07/15/2012 and you wish to add 10 days in it using the below formula:-
Just select the formula portion, as shown in attached picture and press F9 and you will see that the formula has now became as :-
So you got to know the part ouput of the formula even before committing the entire formula and that is the beauty of exceution key “F9″.