I want to be able to toggle the touchpad on and off using the standard Function F3 key.  It does so if I check "Launch Gnome service on startup" in the Session and Startup/Advanced/Compatability, but launching Gnome service causes other problems.  All the other standard function keys seem to operate as expected.  Is there a way to add the F3 functionality?

I am using an ASUS 1015PEM.  I installed Ubuntu 11.10, then installed Xfce (4.8).  synclient TouchpadOff=1 shuts it off, but initially synclient shows TouchpadOff=1 yet the touchpad is on.  Subsequent to my entering synclient TouchpadOff=1 and synclient TouchpadOff=0 the touchpad is off and on respectively as expected.

xev results (pressing Fn F3 key):
KeyPress event, serial 34, synthetic NO, window 0x3000001,
    root 0xab, subw 0x3000002, time 3489713, (44,47), root:(672,258),
    state 0x0, keycode 199 (keysym 0x1008ffa9, XF86TouchpadToggle), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyRelease event, serial 34, synthetic NO, window 0x3000001,
    root 0xab, subw 0x3000002, time 3489713, (44,47), root:(672,258),
    state 0x0, keycode 199 (keysym 0x1008ffa9, XF86TouchpadToggle), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

Results in a text console from showkey -s: 0x74 0xf4

I note that something in the system associates the Fn F3 key with the Touchpad Toggle.  How do I get it to act on that knowledge?

Thanks,
-Denis

More:
xfconf-query -lcv xfce4-keyboard-shortcuts generates a long list but does not include ANY function keys, so I presume that the function key actions are in some system other than xfconf.  Anybody know what and/or where that system is?

Sample of xfconf-query -lcv xfce4-keyboard-shortcuts output:
/commands/default/<Control>Escape          xfdesktop --menu
/commands/default/<Super>p                 xfce4-display-settings --minimal
/commands/default/XF86Display              xfce4-display-settings --minimal
/providers                                 <<UNSUPPORTED>>
/xfwm4/custom/<Alt><Control>End            move_window_next_workspace_key
/xfwm4/custom/<Alt><Control>Home           move_window_prev_workspace_key
/xfwm4/custom/<Alt><Control>KP_1           move_window_workspace_1_key