I have an Excel worksheet where I calculate 3D print jobs - time, filament used, cost, etc. As jobs are completed and paid for, my current practice is to use a strikethrough on that line to show that ...

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 ...