Data Validation blanks for formulas
 

I am using Excel 2007. This seems silly to me, but I don't see an
easy work around. I have a cell that has data validation set be whole
numbers between 0 and 999 and with "ignore blanks" checked. This
works fine UNLESS I use a formula in the cell that returns a blank, at
which point I get a data validation error.

Note that if I manually enter a blank then I do not get an error.

An example of the formula is

=if(A1="","",A1)

I want to distinguish the value of 0 from the value of blank. Is there
a different way to enter a blank in a formula that will be interpreted
as a blank by the data validation?

Thanks,
Rick