Securing Access to other servers

Hi all,

If we have a team viewer session running, can the person viewing the remote screen use RDP or telnet etc to then go to another machine where team viewer is or not installed?

For example....I have several Windows Servers that different customers connect to via the Internet through our DMZ, I may want them to use Team Viewer as a secure method to access the desktop, we can then close TCP Port 3389 on our external Firewall. These servers are on the same subnet. I want to prevent a customer from trying to access another customers server while they are on the desktoip via Team Viewer.

thanks

Dave