Handling keyboard events (trapping modifiers' events)

Hi guys,

I've got quite crazy idea - there's a wonderful button on a keyboard
named Caps Lock. And I really want it to toggle something useful -
like... ummm... keyboard layout? While switching keyboard layout isn't
really tricky, trapping caps lock - that's an issue.

Using examples from ADC, I easily figured, how to catch modifier
status 0x400. Now the question is - but how can I actually disable
capitalizing after that? Ideally, I should catch this event and do not
call something like DispatchEventOn method - but there's no such a
method I can find :) (I am quite new in Mac OS X programming, but not
new in UNIX).

Any ideas?

Best regards,
Roman