User to configure ONLY the APN field

Hi, I need a way to let user configure only the APN field of a 3g Connection.
I don’t want him to be able to give a look at all the others configuration of the routerboard.
I have tried using skins, but I cannot show only the pptp interface to configure, and VPN would be visible too.

Is there a way to achieve this?

P.S. since the gateway would be the 3g connection, I could not configure this remotely.

Thanks all.