Assuming you are going to enter these by date going down the sheet, starting
in row 2, and assuming you have the date in col A and the # of custoemrs in
col B. Then, in cell C3 try

=AVERAGE(OFFSET(C2,-MIN(19,ROW(B2)-2),-1,MIN(20,ROW(B2)-1),1))


"Aaron H" wrote:

> Hello everyone, thanks all in advance for any comments and help.
>
> I have been asked to create a spread sheet for work that tracks the number
> of customers that come into our buisness througout the 24hour day, recored
> the number of customers and then create a rolling three week average. an
> examble of this would be monday april 18th 10 people were in the store,
> monday april 25 5 people came into the store and moday may 2nd 10 more people
> came into the store so the average of this is 3..were my problem is I need a
> way to automatically drop april 18th out of the equation when i put in the
> data for may 9th? is there a way to automatically do this?
> again thanks in advance
> Aaron