Using SIP client through a VPN

[launch]

Hi,
I would know if is possible with Symbian API to create a function that perform a VoIP call (SIP) using an APN related to a VPN (previously created) in a full transparent way from the point of view of the user.

When I say "transparent" I mean without prompt for username/password.

Thank you in advance

Giovanni

[launch]

So it's not feasible?

What are the critical points?

Thank you
Giovanni