Aha! The wonderful Mr Sibly actually pointed me in the right direction with this.
Bascially, the trick is to call ActivateGadget after a button or checkbox is manipulated - this will restore Keyboard focus to the gadget you activate (in my case, the main window).
Bascially, the trick is to call ActivateGadget after a button or checkbox is manipulated - this will restore Keyboard focus to the gadget you activate (in my case, the main window).