If Excel is not highlighting cells in the formula, enable 'Allow editing directly in cells' and 'Enable fill handle and cell drag-and-drop' in Excel options.

From now onwards, Excel will display the formula in all cells instead of the calculated results. Note: If you want to show the results again in all cells, you need to disable this setting.

This article looks at how to use Excel’s auditing tools to audit formulas and ensure the accuracy of data.