title: Use Renderer on VirtualColumn in Admin Grid
body: <p>On previous works, I've overrided the Order grid in the Magento Admin, to display others data. So I've create a module to do so. I  wrote the new block and reported the overriding in the config.xml :</p>
  
  <pre><code>&lt;blocks&gt;
      &lt;adminhtml&gt;
          &lt;rewrite&gt;
              &lt;sales_order_grid&gt;
                   Company_Module_Block_Sales_Order_Grid
              &lt;/sales_order_grid&gt;
         &lt;/rewrite&gt;
     &lt;/adminhtml&gt;
  &lt;/block&gt;
  </code></pre>
  
  <p>After that I've created a new module to get and save new data. I want now to display them on the grid. These data come from a custom table and are not already used in the grid. I've also to use a renderer to display them.</p>
  
  <p>I don't want to make these two modules dependent of each other, the new data have to be displayed on the overrided grid as on the default one. So I want (if it's possible) to avoid an other overriding of the first module by the second one.</p>
  
  <p>By searching on the Internet, I found this interesting article : <a href="http://www.ecomdev.org/2010/07/27/adding-order-attribute-to-orders-grid-in-magento-1-4-1.html" rel="nofollow">http://www.ecomdev.org/2010/07/27/adding-order-attribute-to-orders-grid-in-magento-1-4-1.html</a></p>
  
  <pre><code>$resource-&gt;addVirtualGridColumn(
      'customer_telephone',
      'sales/order_address',
      array('billing_address_id' =&gt; 'entity_id'),
      'telephone'
  );
  </code></pre>
  
  <p>This approach is perfect for me : if the first module is disabled, the data of the second one are still displayed on the default grid, and if the second module is disabled, the grid is still overrided.</p>
  
  <p>It could have been perfect, but it seems you can't use a renderer by using the addVirtualGridColumn method.</p>
  
  <p>So my question is : Is there a way to use renderer on virtual column ? And if not, is there still a way to elegantly add a "rendered" column without overriding the grid ?</p>
  
  <p>Hope I've been clear in the explanation of my issue and hope there's a solution. Thanks for your help.</p>