[Users] Possible to use subst() to alter first line of INVITE?

Evening all! I'm trying to use subst() to alter the first line of an INVITE I'm sending to a remote Asterisk box, although I have been unable to get this working. Perhaps I need to use a different function? The INVITE I'm working with looks like (IPs have been changed to protect the innocent): INVITE sip:s@192.168.1.250 SIP/2.0 Record-Route: <sip:192.168.1.190;lr;ftag=as62d28c09> Via: SIP/2.0/UDP 192.168.1.190;branch=z9hG4bKcce2.b907e716.0 Via: SIP/2.0/UDP 192.168.1.147:5060;branch=z9hG4bK5a287301;rport=5060 From: "lmadsen2#lmentinc" <sip:lmadsen2#lmentinc@192.168.1.147>;tag=as62d28c09 To: <4166289921@switch1> Contact: <sip:lmadsen2#lmentinc@192.168.1.147> Call-ID: 791d9cc101c5cbdd2896c0d357cf644c(a)192.168.1.147 CSeq: 102 INVITE User-Agent: Asterisk Max-Forwards: 69 Remote-Party-ID: "lmadsen2#lmentinc" <sip:lmadsen2#lmentinc@192.168.1.147>;privacy=off;screen=no Date: Thu, 12 Apr 2007 05:00:26 GMT Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, NOTIFY Supported: replaces Content-Type: application/sdp Content-Length: 240 I have two subst() I've been playing with. This one works which alters the To: line in the INVITE: subst('/^To: (.*)sip:[^@]*+(.*)$/To: \1$hdr(X-DID)\2/g'); This one does not, which I would like to alter the INVITE sip:s@192.168.1.250 SIP/2.0 of the header. This is the very first line in the INVITE. subst('/^INVITE (.*)sip:[^@]*+(.*)$/INVITE sip:$hdr(X-DID)\2/ig'); I tested the regex online as well, and it seems to work. Anything I'm missing? Is there another function I can use to alter the line I want, or am I up poop creek? Thanks! -- Leif Madsen. http://www.leifmadsen.com http://www.oreilly.com/catalog/asterisk