Is it possible to write a script or is there another method of backing up a spreadsheet when opened? The reason is: I have other users opening my spreadsheets and if they completely stuff everything up I want to be able to go to a backup created when they first opened my doc. 
Script to Create Copy (Backup) of entire spreadsheet onOpen
google spreadsheets;google apps script
Check out the built-in revision history, that's available in both the spreadsheet and the script editor under the first menu option (File).Read the Google Help for more info: revision history