title: Change row values till first match
body: <p>There is a table with the following structure:
  (Date, Shop, Exists, Status)</p>
  
  <pre><code>2012-10-09  Shop1   0   Trial
  2012-10-23  Shop1   0   New
  2012-10-30  Shop1   0   New
  2012-11-13  Shop1   0   New
  2012-11-27  Shop1   1   New
  2012-12-11  Shop1   0   New
  2012-12-18  Shop1   0   New
  </code></pre>
  
  <p>I need to convert it to the following result:</p>
  
  <pre><code>2012-10-09  Shop1   0   Trial
  2012-10-23  Shop1   0   Trial
  2012-10-30  Shop1   0   Trial
  2012-11-13  Shop1   0   Trial
  2012-11-27  Shop1   1   New
  2012-12-11  Shop1   0   New
  2012-12-18  Shop1   0   New
  </code></pre>
  
  <p>The algorithm is set to trial till Exists column = 1.</p>
  
  <p>There are more Shops, so getting Date value (2012-11-27 in my case) for every single shop doesn't look very sane. Any clues?  </p>