FXRuby and win32 events

I’m trying to build a small ‘auto-copy’ app with FXRuby (on windows). I
need to intercept WM_CHANGECBCHAIN message (in conjonction with win32
function call SetClipboardViewer and ChangeClipboardChain), but it
seems that the only way for handling non integrated win32 event with
Fox is to overload the FXApp::dispatchEvent C function …

Any idea for doing that only with Ruby and FXruby ?