day, limit, trafic

I use pppoe-client conection to internet and one wireleless card as AP for local network.

How I can limit trafic for user, one day=50 mb.

I want make that user from 192.168.1.56 can make only 50 mb (trafic) peer day, and user from 192.168.1.57 can make 80 mb peer day…,
but user need to have unlimited speed.

you can use firewall filter with connection bits field activated and use script that each day resets counters for that rule