Getting information on a specific computer in the network based on username

I was wondering if it is possible to get the IP Address or Hostname of a computer on my network given the logon username.

When I say this, I am referring to other users, whom, if I know their username, I can then get their IP/hostname. Is this possible?

I am looking for console commands such as: nslookup

There is a very useful tool by Mark Russinovich, called psLoggedOn. You can find it here