Excel is having a feature similar to version control system. It is called as Track Changes.
We need to share the work book to make "track changes" work.
Track changes can be switched on by selecting "Track Changes while editing" check box in the below screen which can be opened from Tools->Track Changes->Highlight Changes
In the above screen we can see the options such Where, Who and When (e.g not yet reviewed, since date, since I last saved) which can be selected based on our need.
Once we set Track changes ON, excel will start showing the changes in each cell whenever any user changes the content. It will look like below screen.
And, we can accept or reject the changes by going to below screen from Tools->Track Changes->Accept or Reject Changes...
Now we understand that for using this Track changes the Excel work book should be shared. So if we want to turn off the Track changes we need to unshare the workbook.
You can refer below url which will explain how to turn off Track changes without unsharing the workbook.
This Track Changes feature of Excel will be more useful for doing review of Requirements and review of Test cases.