Can One Password Protect Downloaded Excel Workbooks?

Summary

I am wondering if a default password can be assigned to all downloaded ADF Excel workbooks

Content

The problem with the ADF downloaded spreadsheets is that, although they are protected, they are not password protected.  Consequently, users getting the spreadsheets can change the rows and column by simply unprotecting the worksheet.  

Is there a profile option that can assign a default password to all ADF downloaded Excel workbooks?

Would this be a helpful feature for others?