External monitor on IBM T41 laptop

[Johan Tibell]

I would like to use my somewhat bigger monitor when at work. The
native resolution of the laptop's LCD is 1024x768 and the external
monitor's resolution is 1280x1024. I don't need to use both monitors
at once (I don't want to extend my desktop). Is it possible to
configure X so that I can cycle between the LCD and the external (VGA)
monitor? I can already use Fn+F7 to switch between the two but I can't
change the resolution (even when only the external monitor is active)
to anything above 1024x768. My laptop has a ATI Radeon Mobility 7500
(and I'm using the radeon driver for X).