Aircard and VPN dialup networking

I have a Sierra Aircard 555 that I would like to launch at system startup
instead of after authenticating to the desktop because I would like our
mobile users to launch a VPN connection from the logon prompt.

I have tried nesting the dialup within the VPN connection configuration but
it passes the credentials of the logon screen through to the Aircard
authentication which fails.

Is there any way to prevent the DUN connection from CTRL-ALT-DEL from
changing the credentials? It works when logged into the desktop but not from
the logon screen.

Basically I want the users to logon using a Dialup networking connection
which would be a VPN connection which then would launch the Aircard dialup
using the Aircard's credentials.

Thanks for any help
--
Tiga