I'm assuming that the marconi router is set to bridge mode (ie, it's not doing any firewalling itself).
The easiest thing to do is to setup dynamic dns on IPCop. I personally use dyndns.
That way, you always know what your machine name is regardless of the IP.
Each machine in your green network has an IP address (hopefully either static, or assigned statically via DHCP from your IPCop) - If your GREEN workstation addresses are dynamic, you will have an impossible time trying to do this.
Say you have three machine on your green network: asterix, obelix and getafix for arguments sake. Asterix is running a web server, obelix is your windows XP desktop, and getafix is another Windows XP desktop.
(I'm basically describing my own LAN setup here).
Now, I want to access all my machines for various services from outside. I want to get to the web server on asterix, and the remote desktops on the other two machines.
My IPCop box is setup with a dynamic dns name, so it's always updated with the current ip. We'll call this name ipcop.homeip.dom.
I setup port forwarding in IPCop:
default ip, source port 80 to destination ip asterix, destination port 80.
default ip, source port 3389 to destination ip obelix, destination port 3389
default ip, source port 3333 to destination ip getafix, destination port 3389
Now, to access the web server on asterix, I type 'http://ipcop.homeip.dom' in my browser at work, and voila, I get my web page on asterix.
I want to remote desktop to obelix, so I open up remote desktop, and type in 'ipcop.homeip.dom' and voila, I get a connection to obelix.
I want to remote desktop to getafix, so I type 'ipcop.homeip.dom:3333' and voila, I've got a remote desktop connection to getafix.
It's that easy. If you want to be more secure, I would suggest changing the SOURCE port. The Source port is not actually the port the data is coming FROM, as you would logically think. It's actually the port you would connect TO on the ipcop box, which would then forward through to the DESTINATION port of whatever IP address you specify as the destination.
Anyway, hope this explanation helps.