Hi

Have a look he
http://www.cpearson.com/excel/NoDupEntry.htm

Hope this helps.
Andy.

"Sol" wrote in message
...
I have taken over the maintenance of a spread sheet which describes the
population of a treatment center. Each resident is assigned an ID code.
As
a new resident moves in he/she is assigned the next sequential ID. The
ID's
start as 00001. To prevent the dropping of the lead 0's, my predecessor
formatted these ID"s as text. Since the spreadsheet is resorted several
times a day, I want to make sure that the person responsible for
maintaining
the spreadsheet does not enter a duplicate ID number. The director of the
center is not ready to change to a database. Any ideas?