Disabling ISA Firewall Client via a script

I want to use the MS ISA Firewall client on our network. About a third of our machines are laptops whereby the users can use to connect to the Internet via their own ISP. In this instance the ISA Firewall client would prevent this.

I was thinking about running a script to disable the client on computer shutdown and on startup if it detected our network it would enable the client. Unfortunately I do not know the parameters to do this. Has anyone done this or got any advise?