Count by Group

I have been searching the help files, but can not seem to find the answer.

I am needing to do a record count.... by group.

Example:

Group 1

1 datadata

2 datadata

3 datadata

Group 2

1 datadata

2 datadata

3 datadata

4 datadata

I am trying to get the report to show the count (or line number), but reset on new group. I know I can use a formula as "recordnumber" to show the count, but this is only helpful when there is only one group.

Any suggestions?