Does squid admits ubiquity?

["davide.ferrante@xxxxxxxxxxxxx" <davide.ferrante@xxxxxxxxxxxxx>]

Hello,
i use squid with ncsa_auth to identify my users, but i have a problem 
whith the accounts;
how to prevent users  to connect themselves on different machines  with 
the same account at the same time?
I don't know if  i was  clear....  I've  tried to use  at the same time 
the  same accounts  on different machine and it was possible. I need to 
prevent it, because postal police couldn't believe in ubiquity.....
thanks,
Davide