isolate usb-memorysticks

Hi all,

I have the following problem :
- When a user put in a usb-stick in example port 4 in a usb-hub, I want
only user1 can see and can mount these usb-memorystick.
- When a other user put in a usb-stick in a other port example port 3 in
these usb-hub, only user 2 can see and can mount these usb-memorystick, ...

How can I do this?
It's for use with a multiseatcomputer in a library.

I use ubuntu 10.04 for OS.

I have fixed already the following, when I put a memorystick everyone
can see it and write to it.
Or a other solution : when I put in a memorystick, only the person who
have mount the stick can see and write to it.
But that's not good enough, when person1 put in the stick, and person 2
mount the stick very fast, person2 can see and write and not the right
person (person1).

I'm thinking how I can fix this:
- usb port 4 - automaticly mount to /media/usb4
- only user1 has rights to see and write to /media/usb4

But how can I do this ?
- Can ubuntu linux see on wath usb-port the stick is ?
- Can I set rights to the folder /media/usb4 that only user1 can see and
write it? It must only user1 that can see the items also !

Thanks for help to a solution.

gd