This probably has been said before and relates to spreadsheets in general, instead of only to Excel: Well written spreadsheets, if they have need for formulas, can be seen as examples for functional programming, where a cell takes input from specified other cells and the result is in the cell itself, not modifying its arguments, so that it stays the true result at any point in time. This has some advantages and can give a spreadsheet a set of advantages over imperatively written programs processing the same data. Additionally spreadsheets allow for a very short feedback cycle. Of course there are downsides to it as well.
