Excel number formating...

The Custom format would be something like:
#,##0_);(#,##0_);
The trailing ?;? suppresses the Zero.

Or
You can go to Tools>Options>View and take the check mark out of the Zero values option.

Or
You could also wrap your formula in an If statement:
=If(A1-A2=0,"",A1-A2)

DKlippert,
That worked perfectly. But I have another problem. I'm taking the average (as well as min max) of a column of numbers. I don't want the 0's to be counted in these calculations. I thought by making the zeros show as a blank space, it would not be used in the calculation. But it is. Is there anyway to exclude certain numbers in a formula?

It could be done programatically through a custome VBA function. Just define the array and make sure you exclude 0 values from the array.

Unfortunately, my VBA is a little rusty so I'm not in a position to give you the code but it can be done.