title: Calculation order when iterative calculation (circular reference) is enabled
body: <p>I have set <code>automatic</code> as <code>workbook calculation mode</code>, <code>Enable iterative calculation</code> for my Excel, <code>1</code> as <code>Maximum Iterations</code>, and <code>0.001</code> as <code>Maximum Change</code>. This setting permits thus circular reference in my worksheet.</p>
  
  <p>So I put <code>=D4+1</code> in <code>D2</code>, and <code>=D2+1</code> in <code>D4</code>. Now the values of <code>D2</code> and <code>D4</code> are respectively <code>1</code> and <code>2</code>. Now if I refresh the worksheet, their values will increment by 2 as expected. If I calculate only cell <code>D2</code> (select the cell, edit formula mode, and then press enter), their values will increment by 2 too, whereas if I calculate only cell <code>D4</code>, their values will be reset to <code>1</code> and <code>2</code>.</p>
  
  <p>My question is why the comportment of calculation of <code>D2</code> and <code>D4</code> are different? That means even though they are circular reference, there is still an order (beginning and ending), then what is the rule for Excel to determine the beginning point and the ending point?</p>