Open Excel File S13_Formulas_Tables_Pivot_Start and jump to the Activity Tab.
Create a macro that locates all formulas on the Worksheet and adds an IFERROR formula to the existing formulas.
Note that not all formulas are the same - for example formula in cell J8 is not the same as in H8. This means that you can't just adjust H8 and copy all the way to K22. You need to make sure the existing formulas are not touched.
Don't forget to save the file as a macro-enabled Workbook.
The final macro is included in the completed version of the Workbook: S13_Formulas_Tables_Pivot in Module ProjectActivity.