title: Excel Formula - Map Two Column values with Third Column
body: <p>I have below data in excel spreadsheet</p>
  
  <pre><code>customer_id  old_customer_id    parent_id
  ACF00408     ALL02364           1819
  ADA00856     ALT00420           1824
  ALT00420                        1829
  ALL02364     ADA00856           1834
  ALL00523                        1839
  AME02272     ACF00408           28921
  </code></pre>
  
  <p>How do I map column customer_id and old_customer_id to get their relevant parent_id as shown below</p>
  
  <p>For example if <code>ACF00408</code> is found in both <code>customer_id</code> and <code>old_customer_id</code>, its parent_id should be <code>28921</code> and not <code>1819</code></p>
  
  <pre><code>customer_id  parent_id
  ACF00408     28921
  ADA00856     1834
  ALT00420     1824
  ALL02364     1819
  ALL00523     
  AME02272
  </code></pre>
  
  <p>Tried with =VLOOKUP($A2, $B$2:$C$whatever, 2, 0) but not working</p>