need an error msge when I attempt to enter a duplicate value in a

[Guest]

I am entering unique serial no. in col A. Can I set up a rule which will not
allow a duplicate serial no. entry into another cell?

 

[JE McGimpsey]

See

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

 

[Guest]

Check out the validation in the Data section.
select the area of interest (A:A)
<data><validation><Settings><Custom>
enter =countif(A:A,A1)=1

Set the error alert as you want it

 

[Gary Brown]

If you put a Custom Data Validation as follows:-

=IF(MATCH(A1,A:A,0)<>ROW(A1),FALSE,TRUE)

This assumes that you are putting the serial number in column A, adjus
accordingly if this is not the cas

 

[Dave Peterson]

Chip Pearson has something that can help:
http://www.cpearson.com/excel/NoDupEntry.htm

 

[Guest]

Thanks for the help guys.