On the whole, doing any kind of important work in a spreadsheet is not a good idea. They are the perfect environment for mistakes to spawn and grow unchecked. The European Spreadsheet Risks Interest Group (yes, that is a real organization, one dedicated to examining the moments when spreadsheets go wrong) estimates that over 90 percent of all spreadsheets contain errors. Around 24 percent of spreadsheets that use formulas contain a direct math error in their computations.
