In the Finance world, there is a whole industry dedicated to producing and managing spreadsheets. We’ve all experienced the frustration of well meaning users adding extra lines in carefully crafted sheets, or hiding the guts of a complicated calculation away from prying eyes. We evolve and develop our spreadsheets to make it easy for the end user, and of course to keep the office hacker at bay. The best way to achieve this is to lock down the appropriate cells, and then use Protect Sheet and Protect Workbook with a nice secure password. Job done.