cli for gnome-network-preferences?

[crispibits]

I use my laptop at home and at work.
At work all internet traffic goes through a proxy server.
At home it's a direct connection.
I can alter this using the gnome-network-preferences GUI. this then sorts out any gnome program that accesses the network.
I want to dynamically set this on the commandline though. At home I only use my wireless card, so I can use the /etc/network/interfaces file in Ubuntu to run commands only if the wireless card is brought up.
I can't seem to find any way of setting the proxy server via the commandline though - shurely shome mishtake?

Any ideas?

Thanks, Crispin