Xternal Monitor Resolution Change

ok, running opensuse 10.3 on a dell xpsm1330.

I have a Dell 22' EWP monitor and what I want is when I am at work to connect, and have it run at that 22' moinitors resolution (1680x1050).

If I boot with the monitor connected, it simply stretches the desktop but I dont need/want the laptop screen on, so I connect after login, FN+LCD and the image get's moved to the external monitor (but runs at the 1024 resolution).

So what would be the best / easiest way to do that?

Thanks...