Drupal ahah implementation in form alter

Hi All
I have a node with one field that is a node reference.This field should be set automatically in the form submit when a set of rules (eg:author keyword ,language ...etc) are submitted.

To implement this i am using a hook form alter.In the hook_form_alter I am calling a function named my_rules() with the $form and $form_state variables as parameters.This function adding a fieldset with few form elements, including a button.When the button is clicked a section of the fieldset should updated showing the list of rules as checkboxes.

My problem is that the hook_form_alter does not seem to run in the form rebuild and the fieldset is not getting updated with the list of rules.The only way i can get this to work is to reapply the the function i am running in the form alter after the form is rebuilt in the ahah callback.

My form alter function

 function my_form_alter(&$form,&$form_state,$form_id){
      if($form_id=='my_node_form'){
         my_rules($form,$form_state):       
      }
}

Here is the code in the callback

function my_ahah_callback(){
    // The form is generated in an include file which we need to include manually.
  include_once 'modules/node/node.pages.inc';
  // We're starting in step #3, preparing for #4.
  $form_state = array('storage' => NULL, 'rebuild' => TRUE);
  $form_build_id = $_POST['form_build_id'];
  // Step #4.
  $form = form_get_cache($form_build_id, $form_state);

  // Preparing for #5.
  $args = $form['#parameters'];
  $form_id = array_shift($args);
  $form_state['post'] = $form['#post'] = $_POST;
  $form['#programmed'] = $form['#redirect'] = FALSE;

  // Step #5.
  drupal_process_form($form_id, $form, $form_state);
  // Step #6 and #7 and #8.
  
    $form = drupal_rebuild_form($form_id, $form_state, $args, $form_build_id);

  // Step #9.
  //my_rules($form, $form_state);//NOTE NOTHING WORK WHEN I COMMENT THIS LINE
  $sub_form = $form['auto_feeds']['rules'];
  unset($sub_form['#prefix'], $sub_form['#suffix']);
  $output = theme('status_messages') . drupal_render($sub_form);

  // Final rendering callback.
  drupal_json(array('status' => TRUE, 'data' => $output));
    exit();
    
}