Index Match VBA

Hi, I am trying to use a formula array in vba but am getting a run-time error("Unable to set the FormulaArray property of the Range Class").
I am trying to insert an index match formula and carry it down.
The line of code giving the error is the following.

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oFormatLastRow is a variable for the total number of rows in my worksheet "Original Format". This list in which I am looking up values is on a different sheet named "Deduct Codes"

Question1: Why is the code not working as it is?

Question2: Is there a way to write this using variables instead of row numbers? I ask because my list in "Deduct Codes" could grow and I don't want to have to come back and change this line every time it does. My attempt at this is the following but it was not successful either and gave the same error as above. In the following "dCodesLastRow" is a variable for the total number of rows in the worksheet "Deduct Codes"

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Any help is appreciated,
Thanks

Thank you for the reply. The problem was I was using ".FormulaArray" when it needed to be ".Formula" instead. The 2nd attempt worked as well with the previously mentioned fix.
Thanks Again!