It's easy to add a set of numbers together — every spreadsheet user knows how to use the tried-and-true SUM function to find a total. But what if the sum you're trying to find depends on some sort of ...

I keep running into situations in Excel where I want to calculate a conditional sum, but my criterion is something along the lines of "Include cell B1 if cell A1 is a number, likewise B2 and A2, B3 ...