You have already had some good suggestions.
One of my old blog posts may be of help.
Look at
http://www.edferrero.com/Blog/tabid/...1/Default.aspx
and scroll about half way down - to More on Excel 2007 Conditional Formats
(and Excel 2003)
My blog is a little bit broken at the moment, sorry, but this should get you
there.
Ed Ferrero
www.edferrero.com