Scripting PPOE connection without password dialog / Leopard

Hello everyone. First post; please don’t shoot me.

So I’m trying to write a script that automates the ludicrously complicated process of getting onto a wireless network (Wifi, then PPOE over that, then VPN over that). All seems okay, but the code I stole from here to connect to VPN, while it works for PPOE too, produces a dialog asking for my password each time – despite the fact that the PPOE password is set in the relevant part of the Network pref pane.

Here’s what I have. Any tips on avoiding the password dialog would be hugely appreciated.

 tell application "System Events"
   tell current location of network preferences
       set PPOEService to service "Nomadic" -- name of the VPN service
       if exists PPOEService then connect PPOEService
   end tell
end tell