Please see below directions from Microsoft Office support as a reference for enabling iterations:
1A) If you’re using Excel 2010 or later, click File > Options > Formulas. If you’re using Excel for Mac, click the Excel menu, and then click Preferences > Calculation.
1B) If you’re using Excel 2007, click the Microsoft Office Button Office button image , click Excel Options, and then click the Formulas category.
- In the Calculation options section, select the Enable iterative calculation check box.