That's what was essentially suggested to the OP in his earlier posting, but
I think OP's quite firm <g in wanting it to be also resistant to copy n
paste or drag as well, both of which would defeat data validation.
--
Max
Singapore
http://savefile.com/projects/236895
xdemechanik
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"Sloth" wrote in message
...
Highlight the entire column and click Data-Validation
Under "Allow" select Custom
Under "Formula" enter the following
=COUNTIF(A:A,A1)<=1
Replace all A's with the column selected. i.e. enter this formula for
column C...
=COUNTIF(C:C,C1)<=1