Rodger, have a look here,

http://cpearson.com/excel/NoDupEntry.htm

--
Paul B
Always backup your data before trying something new
Please post any response to the newsgroups so others can benefit from it
Feedback on answers is always appreciated!
Using Excel 2002 & 2003

"RODGER" wrote in message
...
I am encoding a long list of data in a single column. What I would like to
happen is that, the computer should block any data entry that is exactly
the
same as those items entered previously in the same column.

In the list, there should be no duplication of data in any cells in a
column.

Help please? or any advice.

Thank you so much.