SUMPRODUCT using INDEX and MATCH

Hi,

I am trying to use Sumproduct with index and match as I want a table to sum the values for a particular region in column A by the specified month in the column header, I need the sum to update as the month changes in the column header. I have done this before using INDEX and MATCH in the formula but I can't find the old spreadsheet I used it on and I can't remember how to do it! I have attached example spreadsheets the data to be summed is in test book 2 and the test book 1 is where I want the data to show when the month in row 1 is updated the column headers automatically update.

any help much appreciated!

Thanks

In B3

=SUMPRODUCT(('[Test book 2.xlsx]Sheet1'!$B$2:$G$12)*('[Test book 2.xlsx]Sheet1'!$B$1:$G$1=B$2)*('[Test book 2.xlsx]Sheet1'!$A$2:$A$12=$A3))

copy across and down

Thanks John this does the trick!