asterisk users - Dec 2006 - IAX timeout if no ringing

Hello,

Is it possible to set up a timeout for IAX when something like the
following happens?

-- Executing Dial("SIP/someone","IAX2/somewhere|45") in new
stack
-- Called somewhere
-- Call accepted by 1.2.3.4 (format ulaw)
-- Format for call is ulaw

<nothing happens here for 15 - 30 seconds - caller gets tired of 
listening to silence and hangs up>

-- Hungup 'IAX2/somewhere-2'


While the call was accepted, I'd really like a way to give up if there
is no ringing, progress, etc. after 10 seconds or so while allowing the
called party to actually ring for up to 45 seconds IF it does ring.

Any ideas?

Thanks,
Trevor