Sumif based on column headers from source tab that move month over month

Let's see if I can piece this together. It looks like you put all your stuff on one page, but that's not the way it is in the real wold.

I am assuming that in the real world, you go out to some source, open it up and copy and paste it into a spreadsheet page. Column A has the month date. Then the next month you get the next source, open this same file, and copy and paste that information somewhere below the data for the previous month. The data begins a line below the month date.

On the summary sheet, you want last month and current month regardless of how many months are on the raw data sheet. You are only interested in the headers shown on the summary sheet.

Please confirm or correct.

Are the number of locations fixed?

Anything is possible with VBA, but this might also be accomplished using the offset command and dynamic ranges (if location number and names are fixed).

When selecting the criteria ranges I'd like to be able to look at the entire column for row matching criteria and select the entire header row for column criteria instead of restricting myself to a specific cell range but I get an excel resource limitation error.

Would you post the formula that produces that error?

That's a lot of data and SUMPRODUCT would be an array formula. That might be the bottle neck, but it might be something else. Having a look at that formula may save trying to re-invent the wheel ... or a flat tire.

Also are you at liberty to fill in the blanks under the offset date headers in the source data? It's a fairly quick and simple procedure. That might facilitate a SUMIFS solution.