Hi Ruth

I think the following formula will do what you want.
=AVERAGE(INDEX(C:C,(ROW(A1)-1)*7+823),INDEX(C:C,(ROW(A1)-1)*7+830),
INDEX(C:C,(ROW(A1)-1)*7+837),INDEX(C:C,(ROW(A1)-1)*7+844))

Copy down, and it will step up by 7 rows each time

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Regards
Roger Govier

Ruth wrote:
Averaging the last 28 days would be fine if it makes the calculation easier.

Yes to your other question the average would go
=average(c844,c837,c830,c823) then the numbers would role by 7 every weekto
give me the continual last 4 weeks.

I tried to set up a formula that looked at todays date using =now() and - 30
days but I couldnt get it to work I might have been barking up the wrong tree
anyway.