Share workbook and track changes
With Excel built-in tools you can easily work together on workbooks and monitor who, when and what changes made. E.g., track project status and tasks.
1. Choose Tools -> Protection.
2. Click Protect and Share Workbook... that brings up a dialog box with only one box you can check, to prevent those sharing the workbook from turning off change tracking.
You can enter a password that they'll have to know before they can do so.