To use data validation to prevent duplicate entries in Column A, say
Highlight the column and enter the following formula in the appropriat
Data Validation box:

=Countif(A:A,A1)=1


David

--
david
-----------------------------------------------------------------------
davidm's Profile: http://www.excelforum.com/member.php...fo&userid=2064
View this thread: http://www.excelforum.com/showthread.php?threadid=48097