Previous 6 Months Value and use in Sum If Formula taking input variable

Hello Friends

How to get previous 6 month value based on input value. I mean I am looking after a VBA code which will ask for month number (using input box) and then based on the input determine the last 6 months name.

Next, use this variable in my sum if formula.

Please help in using the previous months in my formula.

Currently I am using below code for getting input value

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And, now the sum if formula I am using is below.

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Please help in using the above month variable in my sum if formula. I want 6 different formula for past 6 months from input date

I find a simple way out to resolve this problem. What I did is I added one more column using months formula. Now, I have column BQ with month numbers.

Next, I create a input box option to collect the name.

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But, still my sumif forumla is not working. Please help what wrong I am doing in this formula

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If I remove the criteria pertaining to input box then everything works well.