asterisk users - Jun 2006 - Getting at SIP error with SIP_HEADER() ?

Hi,

when attempting to dial an invalid number with Nikotel this is returned:

  SIP/2.0 400 Bad Request request uri is neighter my realm or a valid dns

and Asterisk prints smth similar on the CLI. However it appears that I 
cannot get access to "400 Bad Request" from the dialplan because this 
error is not part of any SIP header, and therefore the function 
SIP_HEADER won't do the trick.

Right or wrong? ;-)

Cheers, Philipp