I wrote this conditional formatting article almost 20 years ago, with the hope that it would be included in a book. Unfortunately, it never made it. I then published it as part of my Excel E-Experts series. The text files were recently added to this blog.
https://dhexcel1.wordpress.com/2017/01/07/archive-of-excel-experts-e-letter-by-david-hager/
This article was perhaps one of my best works in Excel. So, although it was written long ago, it still contains valuable information that I am sharing here. The following file links are the working Excel file and the article document. Enjoy!