Keymap.xml Key Codes

Where are the key codes for Keymap.xml stored? For example, I have a Logitech Revue keyboard that I am using on my Raspbmc. There are buttons on the keyboard that are not on a standard keyboard (like AVR, STB, and TV power buttons). On Windows I could use EventGhost to capture these key presses, then assign an action to them.

I thought I would be able to do this with Keymap.xml, but I'm not sure what name to assign to them. I was able to remap PageUp and PageDown to VolumeUp and VolumeDown, so I know my Keymap.xml is working.

Could I use xev and xmodmap as described here (http://askubuntu.com/questions/24916/how...tain-keys) somehow to get the names of the keys pressed, then remap them in my Keymap.xml?

Thanks.