Using AHAH in CCK field

Recently I could work with some AHAH stuff for CCK, I think it would be very useful to ppl who are seeking for a solution on how AHAH works on CCK fields, in my problem what I wanted to do is I had a CCK fields one is a select field (SELCT 1, SELECt 2) and the other is Text field (Descrition), so I wanted to hide Descrition text field when I select SELECT 2. ok?
How I achieved it, its very somple work around btw.
1. Created a new module and implemented a hook_form_alter, add #prerender value to callback before render.

<?php/**
* Implementation of hook_form_alter().
*/function MODULENAME_form_alter(&$form, &$form_state, $form_id) {
  switch ($form_id) {
    case 'NODE_FORM': // NODETYPE_node_form
      // We force drupal to cache the form because it doesn't for a node add form

      $form['FIELD_NAME_TO_HIDE']['#prefix'] = '<div id="type-wrapper">';
      $form['FIELD_NAME_TO_HIDE']['#suffix'] = '</div>';
     
      $form['#cache'] = TRUE;
      // callback for the prerender
      $form['FIELD_NAME_TO_ADD_AHAH']['#pre_render'][] = 'field_tipo_pre_render';
      break;
  }
}

function field_tipo_pre_render($element) {
  // now the real form elements are in here as children
  $element['value']['#ahah'] = array(
    'path' => 'ahah-change-type',
    'wrapper' => 'type-wrapper',
  );
  // this part may be naughty
  form_expand_ahah($element['value']);

  // $element doesn't pass by reference, so don't forget to return it
  return $element;
}?>

2. Create menu item for AHAH callback

<?php
  // AHAH callback
  $items['ahah-change-type'] = array(
    'title' => 'AHAH Type',
    'page callback' => '_custom_page_change_type',
    'access callback' => 'user_access',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );?>

3. AHAH callback function

<?php/**
* Callback funciton for type
*/function _custom_page_change_type() {
  // 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('submitted' => FALSE);
  $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_id = $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);
  //change your element here
//  $form['field_valores_description']['#value'] = 'roses';
//  $form['field_valores_description']['#disabled'] = TRUE;
//  unset($form['field_valores_description']);
  form_set_cache($form_build_id, $form, $form_state);
  $form += array(
    '#post' => $_POST,
    '#programmed' => FALSE,
  );

  $form = form_builder('node_form', $form, $form_state);//  print_r($form_state['post']['field_tipo']['value']);
  // Step #9.
  $subform = array();
  $subform['field_logo'] = $form['field_logo'];
  $subform['field_valores_description'] = $form['field_valores_description'];
  $subform['field_enlace_web'] = $form['field_enlace_web'];//  unset($choice_form['#prefix'], $choice_form['#suffix']);
  if ($form_state['post']['field_tipo']['value'] == 'Distribuidor')
    $subform = array();

  $output = theme('status_messages') . drupal_render($subform);

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