When Excel does background checking of your worksheet for errors, it follows a set number of rules. You can modify the rules that Excel follows through these steps:
- Display the Excel Options dialog box. (In Excel 2007 click the Office button and then click Excel Options. In Excel 2010 and Excel 2013 display the File tab of the ribbon and then click Options.)
- Click Formulas at the left side of the dialog box. (See Figure 1.)
- Make sure the Enable Background Error Checking check box is selected.
- Clear or set the checkboxes in the Error Checking Rules area of the dialog box, each of which specifies a different error-checking rule that Excel can follow.
- Click OK.
Figure 1. The Formulas options of the Excel Options dialog box.