If you want to use VNC you need to foward ports. .....
http://www.uvnc.com/addons/repeater.html
If you need remote control without static ip (or redirection), or port fowarding try logmein.
Unless your vnc software can be set to make a static outbound connection to a third party you will need to foward ports.
thats how logmein and gotomypc works.
Logmein is free btw.