1 user account can log on at a time

[eluser]rickoverman[/eluser]
Hi All,

I am trying to figure out how to handle user logins. At the moment i have a login system where a single user can logon on diffrent pc's at the same time.

But now im trying to implement some security that when a user is logged in a specific account on one pc , another person can not logon with the same account on another pc untill the user of the other pc is logged out (or session is expired).

Can someone maybe point me in the right direction?

Thanks in advanced

All the best,
R