title: Compare two excel columns which the most frequently occur in specific date
body: <p>I would like to compare between few columns, what where the <strong>top 5 most popular products in year 2015</strong>.</p>
  
  <p>I have this kind of data flow to work with:</p>
  
  <pre>Client | Product | Date of buy
  ------------------------------
  client1 | A | 15.06.2015
  client3 | A | 04.12.2015
  client5 | F | 15.06.2015
  client9 | G | 15.01.2015
  client2 | G | 15.01.2015
  client1 | R | 05.07.2015
  client3 | G | 15.06.2015
  client1 | F | 05.07.2015
  client3 | F | 15.06.2016</pre>
  
  <p>Results - which products client bought the most with (in same date) the top 5 products communities of them. E.g..</p>
  
  <pre>
   1. Product A + Product H 222 times
   2. Product A + Product E 77 times
   3. Product B + Product O 70 times
   4. etc
   5. ...
  </pre>
  
  <p>Greetz,</p>