The Problem To Be Solved.
A good friend of mine had found that an Excel spread sheet no longer had a formulae in a particular cell. It had a number there instead. This meant that any changes in other cells associated with the missing formulae had no effect on the result in the TOTAL column. He wanted to go back to a time when the spreadsheet had the correct formulae in it. He had many backup files and feared he might have to examine each file until he found when the problem occurred. So I advised him of a quick way to examine his backups using a binary chop method to look at just a few critical files.