Use data validation with a custom allow type, and a formula of

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

--
HTH

Bob Phillips

(replace somewhere in email address with gmail if mailing direct)

"S.G.Pillai" <SGPillai@discussions.microsoft.com> wrote in message
news:2C95E5AE-B84A-4E86-830D-60D503DBFFBD@microsoft.com...
> I have to type many tags one after the other. How will i be able to know
> wheather i am reapeating the same tag which has been already entered. and
how
> this can be prevented.
>
> I need the number of tags to appear in the top most column as i enter the
> tag. is it possible in excel. If anybody can help it would be a great help
> fro me
> bye
> thanks in advance