Column letter in formula dependent on another cell question

Hello Group:

Is it possible to take this array formula:

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and amend it so that the red column letters in this formula would be dependent on a letters in cells FM1 and FQ1? So for instance if cell FM1 had the letter "P" displayed in it, the "Q" in my formula above would automatically change to "P" and if cell FQ1 had the letters "AA" in it, the "AD" in my formula would change to reflect the letters in "AA" as specified in cell FQ1, etc. The quotation marks are not needed in the formula. I would be very grateful for any feedback, even if it's to say it can't be done. Every year I have to manually edit hundreds of formulas to reflect the new column letters, so I'm trying to figure out a way to avoid doing that, by this approach.

Thanks in advance!

Try to replace this:

Formula:

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in your formula, become to

Formula:

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It may help for yr problem