Without seeing how your data are arranged it's difficult to be precise but
there are several ways here.

http://www.cpearson.com/excel/duplicat.htm

Mike

"arad" wrote:

Hello good people.

Im having data tables with a list of records representing mailing list of
my customer.
How can I verify that every record is unique (for example: to avoid sending
two letters to the same customer)

Thanks in advance
Arad