locate windows workstation if you know the username

[offset <offset () ubersecurity org>]

Greetings fellow pen-testers,

Looking for ideas on tracking down a windows workstation if you know the username.

I know that if I run     net send username ""     I can tell that the user is online without the message box popping up 
on their machine (usually), but I'd like to know which workstation a particular user is at for a targeted arp spoofing 
attack against a client.

-off

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