This is just a very quick post, more as a reminder to my future self than anything else, but when summing a contiguous, dynamically-sized range in Excel, it can be orders of magnitude faster to use INDEX in place OFFSET, the latter of which is volatile and is therefore recalculated in response to changes to any other value on the sheet, regardless of its dependencies. This has already been explored by others, but just for future reference, always try to replace:

=SUM(A1:OFFSET(A1,rowOffset,0))

with:

=SUM(A1:INDEX(A:A,1+rowOffset))

That’s all for now!