The best formula I've seen for this is here:
http://www.linkedin.com/groupItem?view=&gid=3843467&type=member&item=78700058&qid=e8bfc676-b12d-49f3-839e-8c11b747c516&trk=group_most_popular-0-b-ttl&goback=%2Egmp_3843467
Hi, Steve!
I'm glad you got it working. I'd love to hear more and what you think of my technique to fill the form?
Regards,
Daniel Ferry
Excel Hero Academy
A simple way of doing this is:
=MOD(SUMPRODUCT(--(($A$1:$A1=$A$2:$A2)=FALSE)),2)
...but you must select row 2 and down before entering this conditional formatting formula.
DO NOT INCLUDE ANY CONDITIONAL FORMATTING FOR ROW 1.