Yes, you can do what you want with the programming cable. Are you sure that's what you have? I believe it's always orange, and it does *not* come with the Davis. You have to pay extra for it - like $70.
If you have the programming cable, then see
this link to download the manual from Davis. It tells what settings in hyperterminal to use to connect to the projector.
Then you do something like [BRI?] to query or [BRI123] to set brightness to 123.
Mike