You can't (at least not in Internet Explorer). It's a gap in
Adobe's implementation of the Flash Player ActiveX control. Any key
that that Internet Explorer uses, you cannot capture.
You can capture keyUp instead of keyDown, but if the
keystroke is one that invokes some kind of browser window (like
ctrl + b = Organize Favorites window), the window will appear
before keyUp fires, so you won't even be able to use that