I'm not sure if this is possible but I keep being amazed at what spreadsheets can actually do so here goes
I have a range of cells (J1 to J19) that are pre-determined height options and I was to set conditions to alert me (say, bright yellow background in A5) if the figure we type in to cell A5 is not one of the 19.


Can it be done?
Thanks
Chris

Set conditional formatting formula for cell A5 as =ISNA(MATCH(A5;$J$1:$J$19;0))

But is there a reason you don't use data validation list with source as $J$1:$J$19 for cell A5 instead? User simply can't enter anything except values in range $J$1:$J$19!

And depending on your regional settings you might want to replace the semicolons in Arvi's solution with commas

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