Want to find the total of every other cell in a column in Excel? You can manually select those cells by holding down Control and clicking, but a little formula magic can get the job done much faster.
Microsoft's Excel Team Blog explains how you can use a little basic mathematics and Excel's array features to add up every second cell. The process is a tad fiddly -- you need to use a special method of entering the formula -- but still much less error-prone than attempting manual selection for more than a handful of entries. Hit the post for full instructions. For more Excel tricks, try calculating the week number or designing floor plans in Excel.
Adding Every Other Cell in a Column [Microsoft Excel Team Blog]