Question : vnc, dynamic ip, firewall

I am trying to connect with vnc from outside the lan but i can't seem to be able due to the changing ip address of my isp. Even with the dynamic ip routing service and port forwarding.
i can't seem to be able to connect to it, i think my settings are wrong or i used the wrong program, can someone guide me to how to do this.
i set port forwarding externally and mapped it to my computer's ip but i don't know how to map it with the no-ip dynamic routing service, since there is a port number there as well. I wonder how do you actually configure your port forwarding to map to your ip routing service? which service should i use if i can't use no-ip and how can i do this? would i have to port forward internally as well?

Answer : vnc, dynamic ip, firewall

Alternative option you may find easier is just to use www.logmein.com free service - it installs a small client on the PC but then you can get remote access through the website without worrying about dynamic dns, port forwarding etc.