Crystal Reports Adding custom column to crosstab

Message

   Hi,
 I have a crosstab with 7 column(for the days of the week). I want two more columns to be added based on the value of the existing 7 colulmns.

Ex:(What I have)

Group       total Sun Mon Tue Wed  Thu  Fri  Sat
aaa             5      1     2    0     0       0     3    0

I want like this

Group       total Sun Mon Tue Wed  Thu  Fri  Sat    #ofdays   Avg per day 
aaa             5      1     1      0    0       0    3     0        3               0.43

Note: #ofdays means, # of days that has non zero.

Can any one please help me???