I copied this from the macrolanguage
http://kmeleon.sourceforge.net/wiki/MacroLanguage2#setaccel()
setaccel( keys [,command]); Since version 1.1
This method can be used to set keyboard accelerators instead of editing accel.cfg.
Parameter Required Type Value Meaning
keys YES STRING A key combination(1) The addressed key combination.
command YES STRING A command(2) The command to be associated with the key combination.
(1) A space-separated list of predefined key names.
(2) Command can be "ID_..." or "pluginName(pluginCommand)". If command is an empty string, this is a deletion.
There is also a file you can edit. Get to the file with EDIT - CONFIGURATION - ACCELERATORS. Same idea here. An empty command should be a delete.
I have not tried either, but I hope one method works for you.