any tips greatly appreciated.

Seek answers on MSDN, MSDN is the source of all win32 wisdom; autoit is also a source of win32 wisdom, especially this kind. Also, see killkeys it catches keys, its open source

OTOH, global keyboard shortcuts aka hotkeys is a very old windows feature, so just use that

hotkey,hotkey -> Win32::GlobalHotkey, Windows Hotkey, Perl Hotkey/Shortcut, Continueing the Quest to get RegisterHotKey to work!