Assume you enter values in column A starting in A2
in B2 put

=IF(A2="","",COUNTIF($A$2:A2,A2)1)

copy down as far you know you will need

If you really need yes or no use

=IF(A2="","",IF(COUNTIF($A$2:A2,A2)1,"Yes","No"))

I would be annoyed seeing all these no entries so I would use
conditional formatting to change the colour of the cell value that
has been entered more than one, select A2 and use

COUNTIF($A$2:A2,A2)1

as conditional formatting then copy down just the formatting with the
paintbrush

or if using another column

=IF(A2="","",IF(COUNTIF($A$2:A2,A2)1,"Entered more than once",""))






--


Regards,


Peo Sjoblom

"Emily" wrote in message
...
Hi everyone,

Column B contains a list of text data, which happens to be numbers (e.g.
1172, 4721, 6743, etc.). Every time I enter a new number in the column, I
would like another column in the same row to check the previous entries in
column B and report whether the exact same number has been entered before
(if
true="yes", if false="no").

It seems simple, and reading previous posts on similar subjects has left
me
totally confused. I tried an IF function but didn't get very far.

-Grateful newbie