This has probably been answered several times but I can't find an answer for the life of me. Apologies for that.

I have a formula in a cell:
=AVERAGE(B3:B14)

When I drag it down to autofill the formula reads:
=AVERAGE(B4:B15)

However I want the formula to jump by 12 rather than by 1 to say:
=AVERAGE(B15:B26)

Does that make sense? I have a long list of monthly data over many years and am calculating the annual average.