Using these forums (which are absolutely brilliant!) I have built the
following formula:

=IF(MID($M6,1,1)="x","",IF(--(COUNTIF($B$17:$B$108,N$4)0)=1,"#",""))

I now have the problem of trying to explain what this does, but that my
question, could someone give me an explanation of what this formula is
saying, in particular the -- section?

Many thanks
--
J