Add numbers by week

[RIKIL]

this might be an easy one...I have a spreadsheet which has a certain date on each row. In a different column I have a number that is related to the date. What I want to do is find the average of each number but only if the date falls in a certain week of the year.

So I am trying to consolidate the numbers that correspond to the dates so I can chart based on a 52 week year.

Ex

3/30/08 55
3/30/08 48
4/1/08 87

in this short example I would want to get the average of 55 and 48 because they are in the same week. I will want to do the same with the rest of the dates in the sheet.

Is that easy or not? Am I just missing something obvious?

Thanks.

[shg]

Maybe like this:

=AVERAGE( IF( (A1:A10 >= SomeSunday) * (A1:A10 <= theFollowingSaturday), B1:B10) )