title: How to ADD latest values if not 0
body: <p>Is there a better way of adding the latest 3 values in a row where the value is not 0 (i.e, skip column when value = 0)? <br></p>
  
  <p>Example :</p>
  
  <pre><code>       [Jan]      [Feb]     [Mar]       [Apr]      [May] 
         [2]        [3]       [10]        [0]        [7]
         [2]        [3]       [10]        [0]        [0]
         [2]        [3]        [0]        [0]        [7]
         [2]        [3]       [10]        [0]        [7]
  </code></pre>
  
  <p>Looking for the row values; 20, 15, 12, 20.</p>
  
  <p>At the moment I'm only thinking of a massive case statement...</p>