title: How to modify a grid in adminhtml in Magento?
body: <p>I'm trying to modify the app/code/core/Mage/Adminhtml/Block/Customer/Grid.php file with my own grid, which is located at app/code/local/MyCompany/MyModule/Block/Adminhtml/Customer/Grid.php</p>
  
  <p>I tried to add this code in my config.xml :</p>
  
  <pre><code>&lt;blocks&gt;
      &lt;adminhtml&gt;
          &lt;rewrite&gt;
              &lt;customer_grid&gt;MyCompany_MyModule_Block_Adminhtml_Customer_Grid&lt;/customer_grid&gt;
          &lt;/rewrite&gt;
      &lt;/adminhtml&gt;
  &lt;/blocks&gt;
  </code></pre>
  
  <p>but it didn't work, can somedboy help me?</p>
  
  <p>[edit] I updated my code with the help of the first answer but this didn't work either, I've got a server error. My grid file works well if I replace my core file [/edit]</p>