Prevent multiple logon to the network.

Hi,
We would like to prevent users from loggin into the network more than once through our wireless AP. We are using a meru link controller which is integrated through AD. We've created guest accounts which is linked to our guest wireless profile. The problem we are having is people are sharing the account and PW so there are multiple logons with the same account to the network. Is there away to prevent multiple logons through AD?