I want to copy down formulas refering to ranges of 25 rows (e.g. sum
rows 1-25, sum rows 26-50 etc.) but when I copy the formula down, it
only adds one to each reference, not 25 (even when I've supplied
several correct formulas). Are there any tricks for getting around
this? I have to copy the formula down 100 times and don't really want
to type each one.


Here's one way.

If the data is in column A, put this in B1 and copy down:
=SUM(OFFSET($A$1,25*(ROW()-1),0,25,1))