Retrieve forwarded MSISDN

[david tejedor]

Hi all,
I'm trying to gather the MSISDN of a forwarded phone call, this is:
PhoneA calls to PhoneB , 
PhoneB has all lost calls forwarded to PhoneC, 
PhoneC recieves the call and is acting as a GPS modem connected to gnokii.

So far I've managed to get PhoneB MSISDN using the monitor program available at 
gnokii-extras, but I need both MSISDNs of PhoneA and PhoneB.
Is there are any way (I don't mind having to deal with programming) to 
accomplish this?

Regards.