Groups total in report footer?

[janis]

I have report like this:
in detail section
date1      - group 1
     data for AM -group 2
     data for PM
   total for group 2
  total for group 1

date2 ...
...
...
...

now I want in report footer to have total for AM data and PM data like this:

Total AM ......
Total PM ......

How to do that?

regard j