Keith,

You can do this with Data Validation. See
http://www.cpearson.com/excel/NoDupEntry.htm for details.


--
Cordially,
Chip Pearson
Microsoft MVP - Excel
Pearson Software Consulting, LLC
www.cpearson.com


wrote in message
...
Is there a way to prevent/block users from entering the
same information more than once?

Example:

John Smith

John Smith (flag to say that data already exists?)

Thanks for your assistance in this matter.

Keith