Use a formula of

=COUNTIF($A$2:$A$209,A2)1

where A2 is the DV cell, and on the Error Alerttab of DV, set the error
style type to Warning

--

HTH

Bob Phillips

(replace xxxx in the email address with gmail if mailing direct)

"Mald" wrote in message
...
I would like to apply Data Validation to entries in a cell to prevent
duplicates, but I need the facility to enter a "valid duplicate" eg When
entering a surname that has been used before a warning is returned but
this
can be ignored if entry is valid.