Adding Averages to Cross Tab

[CJP12711]

I have a table with the below fields:

ID Date
1 3/29/08
2 3/25/08
3 3/15/08
4 3/14/08

I have a cross tab report with a Saturday label as the row, the date (by month)as the column, and a distinct count on the ID number. This all works beautifully. The part I am having trouble with, is adding an average to the summarized field. If there is a total of 4 Saturdays in a month, and January had 16 cases, I want to show the average number of cases per Saturday - in this case, 4. Does anyone have some hints for doing this?

I'm using Crystal Reports 10.

Thanks!
CJ