[Serusers] CPL and billing

Gents, I've been going throught the draft-ietf-iptel-cpl-09.txt to try and find information on doing the following: I want to offer my clients the option to do call forwarding and other smart things with cpl. Now I can not find information on how I can change the source name of the caller. Just to explain: - I am a user and out of the office - I set a call forward to my mobile - some calls me and my cpl script is run - it tells the proxy to route the call to my mobile Who will now be billed for the call ? I can not find a way to change the calling-id. In this case I need to be billed for the outgoing call to the PSTN (mobile). Am I correct to state this is not possible with CPL ? regards, Arne.