asterisk users - Sep 2004 - Queue position and thankyou message plays even when queue is empty?

I'm in the process of setting up a queue system where the position
message and thankyou message are required to play every 90 seconds. 
However, if a caller comes in to a queue with active agents logged in,
and no one else is in the queue, the messages play immediately, and
then the agents are polled.  Is there any configuration parameter that
will disable the playing of the messages if the queue is empty and
agents are available?

-Chris