title: Flex Datagrid Sort Stopped Event
body: <p>In Adobe Flex, when user presses and releases Mouse on a column header in a Datagrid,
  the corresponding sorting function for the column is called.
  Is there a way to figure out, when does the sorting stop?
  Basically, there is a column "Serial Number" in the datagrid,
  which I want to relabel, when the sorting for a particular column
  happens and stops.</p>
  
  <p>I need it because : 
  There is an year column in my datagrid.
  When I sort it, suppose there are 6 entries : </p>
  
  <pre><code>2008
  2008
  2008
  2009
  2009
  2009
  </code></pre>
  
  <p>I want the labeling to be 1,2,3,1,2,3, i.e. the labeling restarts after the year
  changes.</p>