I have a MS excel file that is used to do some very complex and secertive calculation. I need to make it as secure as possible. I have password protected everything and made the sheets with the calculation tables "very hidden". Is there anything else i can do...? I was playing around with doing EFS file sharing but the issue with that is anyone who has access to the file also has to unencrypt the file and email outside the company. The idea is it should be accessible only from the internal network. It should never be email or access by more then the 10 people in the engineering group.