function isChecked()
{
  var form = $('message_form');
  var result = false;
  for (var i = 0; i < form.elements.length; i++ )
  {
    if (form.elements[i].type == 'checkbox')
    {
      if (form.elements[i].checked == true)
      {
        result = true;
        break;
      }
    }
  }
  return result;
}

function updateMessages(update_url)
{
  if(!isChecked())
  {
    new Ajax.Request(update_url, {
	  method: 'get',
	  onSuccess: function(transport) {
	    var messages = $('mailMessages');
	    if (transport.responseText != '') {
	      messages.update(transport.responseText);
	    }
	  }
	});
  }
  setTimeout('updateMessages(\''+update_url+'\')', 5000);
}