one of the documented procedures in this installation of the ACS
events_group_create   db   name   date   location
What it does:
Given an event's name, date, and location, creates a user_group for that event and returns the new group's group_id. Returns 0 if an error occurs
Defined in: /web/philip/tcl/events-defs.tcl

Source code:

    set group_name "$name on $date at $location"
    return [ad_user_group_add $db "event" $group_name "t" "t"]