sorting options with cck and views module using custom argument handling code

I grabbed some code from book pages and put it in my view argument handling code box. I'm trying to add a sort for the custom CCK field "field_price". I tried this but failed, I don't know how to make the view join that table. I don't really know what I'm doing. Can anyone help?

if ($_GET['sort']== "title") {
  $view->sort[0]['position'] = 0;
  $view->sort[0]['field'] = 'node.title';
  $view->sort[0]['sortorder'] = $_GET['order'];
  $view->sort[0]['options'] = '';
  $view->sort[0]['tablename'] = '';
  $view->sort[0]['id'] = 'node.title';
}
else if ($_GET['sort']== "date") {
  $view->sort[0]['position'] = 0;
  $view->sort[0]['field'] = 'node.created';
  $view->sort[0]['sortorder'] = $_GET['order'];
  $view->sort[0]['options'] = '';
  $view->sort[0]['tablename'] = '';
  $view->sort[0]['id'] = 'node.created';
}
else if ($_GET['sort']== "price") {
  $view->sort[0]['position'] = 0;
  $view->sort[0]['field'] = 'field_price';
  $view->sort[0]['sortorder'] = $_GET['order'];
  $view->sort[0]['options'] = '';
  $view->sort[0]['tablename'] = '';
  $view->sort[0]['id'] = 'field_price';
}
return $args;