Set a maximum attendees that can accept a meeting request.

First, I'm pretty sure this can't be done, but it would be cool.
 
We run regular training sessions within the organization. We can only accept a maximum of 15 people in each session.
 
Is there a way I can just set a limit and then send out an Outlook meeting invitations for each session to everyone in the organization and fill the sessions of a first come, first served basis as people accept the meeting invitations.
 
We currently use Outlook 2010 on Exchange 2007 but Exchange is due for an upgrade soon.
 
Svend.