If I select E4 then Conditional Formatting with a rule "Use a formula to decide which cells to format" then I use:
=AND(($B$1="keighley"),(ISNA(MATCH($E$4,$G$1:$G$11,0))))
and select the Format required then it will only format E4 if B1="keighley" and the entry in E4 is not in the range of the MATCH.
I put the range to check on the same sheet but it works as well if on a different sheet. I always use an Excel table for a list source so it's dynamically maintained.
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[TD="align: center"]1
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[TD="align: center"]Keyword=
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[TD="align: center"]keighley[/TD]
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[TD="align: center"]Valid Codes
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[TD="align: center"]Enter Code[/TD]
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[TD="align: center"]4
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[TD="align: center"]Code 7[/TD]
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[TD="align: center"]9
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[TD="align: center"]Code 8[/TD]
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[TD="align: center"]10
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[TD="align: center"]Code 10[/TD]
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