hustla
If using the DV formula is: =COUNTIF($A$1:$A$50,A1)=1
or similar...........................
Remember, that Data Validation is in effect only when the cell value is changed
by the user. It does not catch changes made by VBA procedures, or as a result
of a calculation in a formula. Also, Data Validation does not apply to changes
made when the user pastes data in to the range.
Gord Dibben MS Excel MVP