sortable_element on multiple lists

Hi all,

I have a list of users belonging to a group: (user HABTM groups)

Group 1
- user 1
- user 2
Group 2
- user 4
- user 2
- user 5
Group 3
- user 6
- user 7

I want to enable user dragging between groups. Eg. i want to move user
6 to group 1. The users are ordered alphabetically inside a group. If
I drop a user in a group it would be ideal that it is thus placed
alphabetically (not important though).

Can this be done?