Averages by month

Here's the concept.... on one sheet you have all the dates of each individual day of the year on the left, and then several colums of stats and numbers... looking kind of like this...


----- A ----- B ----- C ----- D ----- E
1/1/01 | 1500 | 6 | 8 | 42
1/2/01 | 1652 | 4 | 9 | 36


On another sheet, you have a chart that is taking monthly averages of all those numbers and showing them.... so you have something like

January | Average from row 1 through 31 on column B from the other sheet | " but column C instead, etc.

The issue with this forumla is that if you have it like this =Average(B1:B31) , and then try to drag that forumla down, for the month of February your forumala would read =Average(B2:B32). Does anyone know of a way that I could incorporate date functions in some way so that the formula could just be dragged down for the whole year, and thus only have to be typed once instead of hundreds of times?

Why not use a PivotTable with dates grouped by Months?