Have You Allowed Room for New Data?

It's critical to allow for expansion and editing after you have assembled your worksheet. It's generally a good idea to add a few extra rows and columns to the detail area and to keep totals separate from the detail data by a row or column or two, if possible. One of the most common editing actions you'll perform is inserting new rows and columns. Excel has gotten a lot smarter about this over the years, making obsolete some of the rules of thumb that we old-timers have collected. But it's still possible to mess up.

A rather famous folkloric tale tells the story of an accounting person who inserted a row at the bottom of a range of cells but forgot to adjust the totals formulas and was fired because his numbers were off by $200,000. The moral: Edit worksheets carefully, and always guard against introducing new errors along the way.