Not sure what you mean by a "real"IP address.
do you mean assigned by a DCHP server?
You can have multiple IP's for a single NIC.
ie; your have a static IPin the "private " range
(10.0.0.xx~255.255.255.0) for your LAN (and you could use NetBEUI, for added security) then setup your Vnc and allow it to bind to the same physical adapter. and allow it to use the DCHP of whatever system you are networking to.

Or you could use a proxy?
Or maybe I just don't understand what you're asking?