asterisk users - Sep 2005 - Handling SIP 404 event

Hello all,

I am curious, does anybody know of a way to handle the SIP 404 event?
(ie: is this stored in a variable somewhere, so one can handle it in
the dial plan).

For example, dialing an invalid number on another softswitch on the network:

    -- Executing Dial("SIP/sip7110-8118",
"SIP/7234@softswitch|60|r")
in new stack
    -- Called 7234@softswitch
    -- Got SIP response 404 "Not Found" back from 172.16.23.31
    -- SIP/softswitch-791b is circuit-busy
  == Everyone is busy/congested at this time

At the moment my dialplan logic will respond with "nobody is available
to take your call at the moment. goodbye", unless that extension has a
mailbox. I'd like to be able to branch out and play a different
message when a 404 is received.

Thanks,

Shaun