Hi Dale,
That's currently not possible. The closest workaround would be hack--
create a screen overlay and update its position on mouse move. Even
so, you still won't be able to hide the cursor. There's a relevant,
but not perfectly identical, feature request at:
http://code.google.com/p/earth-api-samples/issues/detail?id=21
Feel free to comment on that one or you can just create a new feature
request if you'd like.
- Roman