Data Validation

[Amy]

I am using the formula:

=COUNTIF($A$1:$A$2000,A1)=1

for my data validation to prevent users from entering the
same value twice in a certain column.

The only problem is - it doesn't work if you type the same
thing into a blank cell - only the cells that already
contain data.

Any suggestions on how to fix this? Any help would be
very appreciated!!

 

[Peo Sjoblom]

Select A1:A2000 with A1 as the active cell,do the validation and use

=COUNTIF($A$1:A1,A1)<=1