The Excel 101: you update an input, then spend the next 10 minutes jumping between tabs to see how it affected your key data. You then update another input, and it’s rinse and repeat. If only there were a way to see the impact immediately! Luckily for you, the Watch Window lets you do exactly that, even if your formulas are in far-away worksheets or workbooks. Here’s how to use this game-changing tool.