OT: Disabling input devices in XF 4.0.1

[Juergen Fiedler <juergen@fiedlerfamily.net>]

Hi,

I have a machine running Woody with XFree86 4.0.1. It has two input
devices: One PS/2 glidepoint and an USB trackball. Now, I would 
like to take advantage of the new input device dialog in The Gimp.
If I disable core events for the trackball in XF86Config-4, it
works OK: I set the input mode for the USB device to 'Window' and
the cursor movements of this device are restricted to the current
window.
But: Most of the time, I would like to use the USB device as a 
regular XWindows input device. And I'd rather not restart X every
time I switch the USB device from The Gimp to a generic X input
device.
So, my question is: Is there any way to turn the sending of core 
events of for a particular input device under XF 4.0.1 without 
restarting X?

Thanks in advance,
Juergen