KVM Switch for a macbook?

At the moment I've got a macbook and a Vista desktop, and I'm using an external monitor that has a resolution of 1280 x 1024. Will any old KVM switch work so that I can use it with both machines, all the ones I've found seem to list every OS apart from OS X as compatible?

The monitor is VGA and going into the macbook via an adaptor.

Could anyone recommend a switch that's going to work? Preferably as cheap as possible, under £30?