Control FortiClient Access

I have configured my VPN portal and have my RDP session working fine.  I have also tested our FortiClients and they seem to connect fine. My new issue is how do I control which FortiClients connect?  I would like to only allow my clients to use their company provided computer to connect via FortiClient.  If they need to connect via their personal computer, they would have to use the portal. 

Can I filter it to only allow clients from a specific MAC address on the computer? I was thinking about issuing a certificate, but I dont know what would keep my users from just copying the certificate to another computer.