in Asterisk 1.2; Asterisk 1.4 users see QUEUE_MEMBER_COUNT()
Returns the number of agents (as opposed to number of callers) in the specified queue.
; Number of agents in "supportqueue":
exten => 123,1,Set(foo=${QUEUEAGENTCOUNT(supportqueue)})


Internal help for this application in Asterisk 1.4:
  -= Info about function 'QUEUEAGENTCOUNT' =- 


Count number of agents answering a queue

Returns the number of members currently associated with the specified queue.
This function is deprecated.  You should use QUEUE_MEMBER_COUNT() instead.
diff output to internal help in Asterisk 1.2:
-- not available in Version 1.2 --