If the two Excel workbooks have the same name, you cannot open them at the same time. For this, either close one of them and then open the other or change the name of one of them.

But before showing you the error, let me describe how—and why—names are used in Excel. Giving names to cells, or even groups of cells, makes Excel much easier to use. For example, it’s far easier to ...

According to a study in the journal Genome Biology, around 20 percent of genetics papers, have errors that have been introduced by Microsoft Excel or similar spreadsheet programs. The researchers ...