Use Mac Address for sheet protection
Many more are now realizing that the excels protect capabilities are not so good. How about using a computers MAC address to protect documents. Not VBA, not passwords but the physical address of a computer. I know people can spoof this though but wouldnt it take some real pc wizards to do so and people who are really trying to get into a document to edit it.
The point is so that we can safely distribute and time expire excel documents and only let certain people view and edit what we want them to and hide everything else.