You won't be able to protect the .csv file with a password in Excel.
The .csv file will only contain values - all your formulae and any
formatting (colours, fonts, lines, column widths etc) will be lost when
you save it. In Explorer you can change the attributes of the .csv file
to make it read-only, but I'm not sure how useful this would be, as a
User will load it into Excel and save it as an .xls file (or as another
..csv file).

Hope this helps.

Pete