Take a look at the following formula

=SUMIF('DP180'!$B$3:$B$52,Total!$A3, 'DP180'!C$3:C$52)

Here, I am searching down the B column in sheet DP180 for values
matching Total!A3. I then sum the corresponding numbers in the C
column.

I would like to do this across multiple sheets - however, the only way
I can do so, is

=SUM(SUMIF('DP180'!$B$3:$B$52,Total!$A3, 'DP180'!C$3:C$52),SUMIF
('DP181.....))

There must be a more elegant way to do this. I've tried putting a
range of sheets into the SUMIF, but that doesn't work. Quick googling
seems to suggest SUMPRODUCT, but I'm not sure how that works, and even
copying simple examples to test SUMPRODUCT results in errors.

Regards,
kwyjibo