Its a boring train journey so Ive cracked the netbook out just for you 😉
Ive tried anywhichway and cant get complex sum functions to operate across sheet ranges. But you can still use the simple sum function across sheet ranges. So What Id recommend is pasting a SUMIF function in a consistent location across the 15 sheets (lets say AA1 for now)
=SUMIF(A1:A10, “UDL”, B1:B10)
This sums the values in B next to incidences of UDL in column A for example.
Then in an end sheet you can use the following formula to sum all of the results in the AA1 cells in all 15 sheets:
=SUM(sheet1:sheet15!AA1)
where sheet 1 and sheet 15 are the two end sheets in your workbook range of 15 sheets.
Not ideal, but robust and simple to audit.
I tried getting the SUM of sheet range functions to use SUMIF etc but it doesnt like it, even as an array forumla. Someone with more experience may know a work around.