If you've ever found yourself copying the same formula down hundreds of rows in Excel, you know how tedious it gets. The usual approach, dragging formulas, adjusting cell references, and hoping ...

A few months ago, I opened one of the formulas in my sales sheet and stared at it for a second too long. It read =G15*0.05. The 0.05 could've been a tax rate, a commission, or a number I'd typed in by ...