How do I get to this dialog box?
From X Manager or X Manager for Domains
Click Tools > Keyboard Maps.
In the Keyboard Maps dialog box, click Reserved Keycodes.
Administrators can also configure Keyboard Maps from the Domain Definitions tab.
Use this pane to specify keycodes that should not be used in the keymap.
In the X Window System, every individual, physical key is associated with a number in the range 8255, called its keycode. A keycode only identifies a key, not a particular character or term among the ones that may be printed on the key.
In general, the default list of reserved keycodes should not have to be changed. However, some system applications ignore the contents of the keymap and intercept particular key codes. To prevent keys from being inadvertently mapped to such a key code value, click the + sign to add that key code to the list of Reserved Keycodes.