RSVP - ability to cap attendance?

Hello,

I'm very new to the CollectiveX world - asked for recommendations for groupsite alternatives to Yahoo, and was glad to discover your site. 

The RSVP functionality was a "must have," and I'm glad to have it, but my request for additional functionality would be the capability for me as a group owner / manager, to be able to limit the number of people who can RSVP.  In our case, we'll be holding group events at another member's restaurant, and have space / headcount limitations. 

In my ideal world (yeah, right?) when I or my fellow managers set up a calendar event, we'd like to be able to quantify the maximum number of people who can attend, and once we hit that magic number, CollectiveX would not allow any further attendees to RSVP, and instead of the Yes/No selection would display a message to the effect that the event has reached it's headcount limit. 

If this funtionality does exist, please accept my appologies for the post, and please let me know what I can do to cap attendance on an already-created calendar event!

Thank you,

Heather