Excel Formula auditing tools
    Excel
    
      2016
      
    
  
  
  
  
  
    If you would like to understand better how some of these complex array formulas work, consider using a handy
            tool - Formula Evaluator:
  
  Select the cell that contains the formula, and on the Formulas tab, in the Formula Auditing group, click Evaluate Formula:
            In the Evaluate Formula dialog box:
            - Click the Evaluate button repeatedly to see the intermediate results as the formula is being calculated. The result of the evaluation is shown in italics.
 - If the underlined part of the formula is a reference to another formula, click the Step In button to display the other formula in the Evaluation box.
 - Click the Step Out button to go back to the previous cell and formula.
 - Click the Restart button to see the evaluation again.
 
See also this tip in French: Évaluer la formule dans Excel.