Configure 1390 WLan to disable on hardwire connect

Have several Latitude D531 laptops running Vista Business at our school. They
all have the 1390 WLan mini-card. I cannot find the setting in the wireless
card configuration to disable the wireless connection upon hardwire connect.
As it stands now, each laptop is getting two IP addresses.

In XP there is an option to "Disable upong wired connection" -- easy to
understand. Can't find anything like that in Vista.

Yes, I can push the button to turn off the wireless (it took the laptop a
couple of minutes to connect to the local LAN on the hardwire) but that is
something most of our teachers just won't remember to do. (Getting them to
'switch user' is going to be troublesome!)

Thanks for any help.
Lynda Young
Weimar Hills School, CA