Hierarchy of Groups?

#1
100 people attended one of our events. I created a group for them, and our programmer added each of them to the new group based on a spreadsheet of email addresses. I used the ACP to send out an email to each member of the group, announcing a special forum section just for attendees of this kind of event.

This works fine, but the event will be repeated, and I need a way to find _new_ attendees who _haven't_ received the "welcome and here's you special forum section" in order to email them all.

My solution - create a new group for each similar event, each group with rights to the same forum section. (Multiple events, same forum section.)

This will grow tedious to administer when I have 10 groups, named "special event 1", special event 2", etc., if I want to change rights, etc. What I'd like is the ability to administer this in a more central manner.

I cannot use forum join date, since many of the attendees will be long-term forum members. I would need something like "added to this group after this date" in the search interface for the bulk email, or a heirarchy of groups to be able to change rights for the child groups.

Suggestions appreciated.

Thanks in advance.

-S-
 
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