Is it possible with VAD to build a IVR to give the possibility to users to record a destination number for a blind transfer on their extension (when the call is not answering for example)?
That API also allows you to update an extension settings. So you could use it to change the forwarding rules for that extension. You would have to download the documentation package from that link and check it out. Please note that 3CX DOES NOT PROVIDE DEVELOPER SUPPORT for this API.