XP won't automatically switch networks

Here is the setup

I work at a utility company and our trucks have satellite modems in them for
communication with an app.

XP SP2 Tablet laptop connects to the satellite modem on the truck via
802.11b - in a Peer-to-Peer connection

I am trying to setup the laptop so that it can connect to an AP
automatically when it comes in range. I would like the Access Point to be
the higher priority and connect to the AP whenever it is availiable and then
switch to the Satellite modem connection when it can't connect to the AP (to
save money on satellite communications)

The problem is that in testing I can get the XP Zero config to jump to the
Satelite modem when the AP is out of range, but I can't get XP to
automatically switch back to the AP...
The problem is that the peer-to-peer satellite modem will never be out of
range of the laptop...but I want it to jump to the AP whenever it sees it..

The AP is the higher priority device and it is first in the list....but once
it is connected to the peer-to-peer connection i can't get it to jump to the
other connection.....any ideas..

hopefully this all made sence - if not please ask more questions...thanks!