I there all

I just got my first Web server up, I got FPSE 2002 and PHP up a running. I was wondering if there was a way i could set a limit as to how much space is available for website that i put on my server. Like they are only limited to 50 megs of space. But i want to be able to configure it per request.(If they want 100 megs and someone else wants only 50megs)

Any ways i have Fedora Core 3, with apache 2. something whatever the latest is.
If someone could help me with this or point me to a website that talks about this in detail i would appreciate it.