[Hampshire] Switching keyboard layouts

Hi all

I've had a quick glance around the interweb but not found anything concrete,
so thought I'd ask here for some tips.

I'm in the US at the moment, and use my UK laptop for most of my work. I've
just picked up an old MS Natural Pro (I love these things), but it is - of
course - US layout. I'm using Crunchbang (Debian Squeeze based) with xfce
and wondered if anybody knows how to automate switching of layouts in some
way.

What I'd -really- like is to be able to plug in the keyboard and have that
one set to US layout, with the laptop keyboard on UK. However I imagine
that's overly hopeful. Does anybody know a way I can detect when the
keyboard is plugged in, then switch the layout... switching back when it's
unplugged?

Or am I always going to have to manually switch :)

Any pointers in the right direction would be appreciated!

Cheers

M