Crystal Reports Adding an average as the grandtotal in a Crosstab

Message

   Hi, 

I created a CRXIr2 crosstab report. 

In the customize style tab of the crosstab export, there is a Grandtotal option for the rows and columns. Instead of summing up my metric, I would like to get the average to be displayed in the Grandtotal column. 

Any tip ? 

IE. The resulting crosstab, 

Type  Jan   Feb   Mar   Total 
----+-----+-----+-----+----- 
A      10    20    30    60 -> 10+20+30 
B      40    50    60   150 -> 40+50+60 

The desired result (the total should be average of the 3 months), 

Type  Jan   Feb   Mar   Total 
----+-----+-----+-----+----- 
A      10    20    30    20  ->  60/3 = 20 
B      40    50    60    50  -> 150/3 = 50 