Take a look at

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

In article ,
Bugaglugs 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?