The router should have a check box for "allow remote administration", followed by an input for a WAN address.
This means that you allow a single WAN address to access your modem interface (port 8080)
So you'd obtain you work IP address (www.whatismyip.com) and input that into your modem when you get home.
Only problem is that your work may not have a static WAN IP address.
So once setup you will be able to access your home modem by inputing along the lines of
<a href="http://203.155.25.79" target="_blank">http://203.155.25.79</a> etc.
Ultimately its best to access your home computer then the modem locally. You achieve this by forwarding a WAN port of your choice (ie 34998) to LAN port 3389 on yourPCs IP (ie:192.168.1.21) address to access it remotely via MSTSC.
Hope that makes sense.

Kirbo.