How to switch to external bluetooth keyboard

Hi

My Asus eeePC901 has a German keyboard.
I have installed Ubuntu over 2 years ago and currently run 11.04 on it.

Although I can switch to the US keyboard layout, I have to remember which keys are changing.

To avoid this and for other reasons I have purchased a bluetooth keyboard.

The bluetooth wizard in System> Preferences lets me install it OK and I can click the bluetooth icon and connect.

However, I cannot work out how to switch from the internal to the bluetooth keyboard.
I have tried Preferences>keyboard>layout>keyboard models but none of the Brands/Models work.

Can anyone advise me how to go about switching when I need to ??

Thank you
Franz