To make it way easier why not do away with Windows Remote desktop altogether.
Team Viewer is now regarded as the number one software for this purpose.
It bypasses all firewall and port rules and you wont need to set up anything other than
an install of the software on each machine. Basically, you would be able to
store the parter id's (office machines) and access them at will.
Check team viewer out here: TeamViewer - Free Remote Access and Remote Desktop Sharing over the Internet