Wow, no-one answered you for more than a year? Have you managed to solve your problem?
I have a much easier way to see who worked how much, and when they were on breaks than comparing and analyzing excel sheets. I use a free software which logs when the employee signed in to work, out to lunch, back and off at the end, also how long they were idle during work hours, and it takes screenshots every 5 minutes. You just need to register and the employees install the programs onto their computers. Their website is myteammonitor dot com.