I have Kubuntu Hardy installed with libx11-data-2:1.1.3-1ubuntu2.
This package contains /usr/share/X11/XKeysymDB.
This file however doesn't have an entry for XF86MonBrightnessUp.

So, if I enter:
$ xmodmap -e 'keycode 101=XF86MonBrightnessUp'

I get:
xmodmap: commandline:1: bad keysym name 'XF86MonBrightnessUp' in keysym list
xmodmap: 1 error encountered, aborting.

SunVideoLowerBrightness doesn't work.
How can I get brightness adjustment mapped to a keycode?