MeetMeCount() — Counts the number of participants in a MeetMe conference
Plays back the number of users in the MeetMe conference
      identified by confno. If a variable is
      specified by the variable argument, playback
      will be skipped and the count will be assigned to
      variable.
; count the number of users in conference 501, and assign that number 
to ${COUNT}
exten => 123,1,MeetMeCount(501,COUNT)