Dual Network Use, Domain @ Work, Cabel Modem @ Home

I work at a high school that has a domain network. At home
I use adelphia cable modem to connect to the internet. I
know there is a way to configue the computer to ask me
upon booting if i am home or at school and the network
card will configue appropriately. I know this can happen
because a teacher at the school does this but was walked
through the configuration by someone that is not around
anymore.

Any help with this would be very much appriciated.

Thank you,
Steve