Hi Max,
You are correct, i hadn't considered that. This is the only other solution i could come up with. The only issue with this formula is that Excel functions that have a Letter followed by a number would be highlighted incorrectly.
an example of a function i am referring to is =DAYS360() or =LOG10(). The conditional formatting would treat that as a cell reference to cell S3 and G1 respectively.
Now there are very few functions in excel that use numbers in their name, and they are pretty uncommon unless you are in the engineering or statistical industry.
As for the included formula. This will work with cell references and absolute cell references.
I could not think of another way of showing that a letter and number combination is = to a cell reference other than the below formula which makes a list 468 in length concatenating A-Z,1-9, and $-"blank".
Conditional Formatting Formula entered same way as my original answer:
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