I'm using Excel custom data validation to restrict entry in A2, if A1 is 0 or blank. The formula =A1>0 works just fine if A1 is a number greater than 0, but if A1 is blank, the restriction does not work. Put another way, I want a blank cell In A1 to be treated as if it was a zero. I've tried removing the checkmark in the box beside Ignore Blank in the validation criteria window but that does not solve the issue. Is there a formula for this?