Take a look at

http://cpearson.com/excel/duplicat.htm#InOneNotOther

In article <68E76A28-F888-4EC2-8782-C2FD2B019772@microsoft.com>,
Bugaglugs <Bugaglugs@discussions.microsoft.com> wrote:

> I've got a list of all the sales accounts that our company deals with in
> column A and all the ones that have been dealt with by my team in column B -
> I want to see which ones from 'A' haven't been seen by my team (i.e.
> potential new opportunities).
>
> Is there an easy way to do this?