VNC to a private IP

[keezel]

I'm not entirely sure which forum this belongs on, so I apologize if this is the wrong one.

I use VNC pretty frequently at work, but I have never VNC'd into a box behind a regular linksys/dlink consumer grade router that assigns IP addresses in the private range (192.168.0.X). I understand that this is a more secure way of doing things, but suppose I wanted to VNC into a PC with one of these private IP addresses? I have the WAN and Gateway IP addresses for the router, and even the internal private IP, but there is only space enough to enter one IP address in the VNC connection box. Any tips?

*Edit*

I noticed the WAN IP assigned to the router is using a 21 bit mask, which leaves me 11 bits to subnet, right? So could I create an IP addressing scheme for whatever hosts are on this private network so long as my subnet mask is more than 21 bits?