Conditional formatting

http://chandoo.org/wp/2008/03/13/want-to-be-an-excel-conditional-formatting-rock-star-read-this/

Go down to the section about highlighting where there's an error. That's the basics of what you want to do. Now you need the code:

This will set a value of "True" if the string is -not- found inside. So if you want to flag it for finding the word NOT, you want the conditional formatting to kick in if the value of this is FALSE.
=iserr(find("NOT",A1))