Cannot route ports for RDP

Hi
I use Belkin wireless router at home. (Firmware Version:
F5D7230v4_UK_6.00.14 , Hardware: 4.00.01).
Sometimes I need to use my home PC from my work through Microsoft RDP.
To have my internal home network more secure - I decided to connect
with the RDP using port routing (for expample 13390 external) -> 3389
-internal).
Here is the link how my configuration looks like:
http://www.net-extend.pl/internal/files.nsf/id/rdp

Unfortunately - there is no way to do it so :( When both ports
(external and internal) are the same - it works great, but when I try
to change one of them - no way!

There is no personal firewall installed. When connecting in RDP client
- I remember to enter the port number (for example: my.host.pl:3390). I
also know how to change default RDP listening port in Windows (in
windows registry key).
So the problem is somewhere else.

There is no firmware update for this product.

Please - help me: where should I look for solution?
Thanks in advance

Marek

So just change, or add, the port the PC uses to accept the RDP sessions.
You're not stuck with just 3389. I've seen setups where several outside
port numbers were each redirected into individual PCs, each running an RDP
server on that corresponding port. Thus the router just redirected port A
to IP address 1, port B to address 2, etc.

Search technet for how to add ports to RDP.