It is simple you have to register for keyboard global hook
SetWindowsHookEx(int idHook, KeyboardHookProc callback, IntPtr hInstance, uint threadId);
in your form and run this form in hidden mode.In callback of you global hook event copy the key you required and forward it to next hook using
CallNextHookEx(IntPtr idHook, int nCode, int wParam, ref KeyboardHookStruct lParam)