You can set notifications to find out when your collaborators have modified your spreadsheets, and learn what sheets or cells they've modified. You can also choose how often you'd like to be notified.
Samsung Android devices such as Galaxy S2 or S3 come with a cool app called Kies Air, enabling you to connect via WiFi connection and manage them using a web browser.
If any file can not be deleted, then you can use the program LockHunter, which removes the active connections of other applications to that file, which allow you to change or delete file.
