Isolating a single program

Hey there. I have a wireless broadband package that charges me if i go over a fairly low limit.

I’m hoping to be able to use this software to block access to absolutely everything except firefox. This would mean I would have control over how much bandwidth i use - at the moment i connect and svchost and windows update starts downloading at about 200kb/second, and i tear through the megabytes.

So what I am hoping: is there a way to just set it to “block everything except this specific program”