For the Every ten minutes, that's a built in function of Excel.
You want to go to Tools --> Options --> Save (tab) and then set the autorecover time. You may also want to make note of the path.

Also, for your second issue, if a document has been changed, An office application will prompt the user to save the document when they try to close it. So what you need to do is tell the staff to click yes when it asks if they would like to save changes on close.