referencing a field in a node in hook_node_api I am using drupal 6. I have a simple question:

Here's a snippet of code from my hook_node_api function:
...

case 'presave':
    {
        if($node-&gt;type == 'example')
        {
            if($node-&gt;content['field_alert']['#value'] == TRUE)
            {
                //do something
                drupal_set_message('Your update will be emailed out.');
            }
        }
    }
   break;


I want to reference the value of a field named field_alert inside of a node type "example" but I'm doing it properly since its not working. How do I do this?
If memory serves it should be something like this:

if (!empty($node-&gt;field_alert[0]['value'])) {
  //do something
  drupal_set_message('Your update will be emailed out.');
}