[Marty_Mcfly]

Hi
Three of us use a desktop PC to get internet access sharing a single connection. Being the oldest, I would like to control over the amount of internet used (per month, in GBs) for each user, although I wont care much about the contents of download (as one of them is a student).

Is there any software / hardware to stop each user from accessing internet after certain amount of download? This will help me to stop them from using my share of usage allowance.