Reference last column in worksheet

Greetings,

I'm trying to dynamically reference the last column using

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. I can't seem to figure out how to convert the column reference from a number to a letter.

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These other methods have failed as well.

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Greetings,

I have a function which converts a column number reference to a letter reference. However, when I try to pass that converted column letter reference using

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or

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, I receive a "Run-time error '1004'." I've tested the function using:

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and it correctly displays the column letter.

Below is my macro and function:

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why not use a column number instead of a letter
something like this

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The function and macro work correctly. I made the mistake of having put them in a worksheet Microsoft excel object. Thank you very much everyone for your help.