I just tried: AND(NOT(ISNUMBER(SEARCH("check",$E18))),NOT(ISNUMBER(SEARCH("cash",$E18)))

which is very similar to what ChemistB did and the same rows got shaded red... but those rows still include many that only have "check" in the E column. Quite confused as to why that is the case... some random rows that had nothing in the E column also did not get shaded while a lot of them did.