I know a manufacturing plant that used an Excel spreadsheet to do all its production planning. There was only one person who understood the spreadsheet and cou

I know a manufacturing plant that used an Excel spreadsheet to do all its production planning. There was only one person who understood the spreadsheet and could modify it, a consultant who made more than the plant manager. "Understandable and fixable" depends more on the complexity of the application rather than the fact it's in Excel.