I am working to protect a fairly simple excel spreadsheet from casual users. My first attempt used an expiration date but that is not satisfactory for several reasons. Does anyone know of a way I could add some sort of Feedlot Tracking CG Vs 3 tpk working copy march 30 kill date.xlsmpassword protection to my spreadsheet such that after a predetermined period of time, the spreadsheet would ask for a password (and provide administrator contact information) and the administrator could then decide whether to allow the user to continue using the spreadsheet or not?

I've attached the spreadsheet with the code for the experiation date, could an administrator over-ride be added or is there a better way?