Apr 25th 2012
From within the Save As dialog box of Excel, click the Tools menu, and then choose General Options.
Click the checkbox to Always Create Backup to have Excel automatically create an .xlk version of your file. For instance, if you save the workbook as Participant Hours Tracking.xlsx, each time you save the file Excel will create or overwrite a second workbook named Backup of Participant Hours Tracking.xlk.
The backup copy is only as old as the last time that you saved, so if you compulsively save every five minutes, your backup will always be five minutes old, but it does offer a bit of a safety net.