Retrieving Parent Subject from Dynamics subject tree

Hi all

I am using subject trees in Microsoft Dynamics CRM, is there a way of retrieving the parent subject of a selected node.

I managed to grab this code off the net which populates the value but cant determine the parent subject, just wondering if there is a property which holds this information that I am missing.

var lookupItem = new Array;

// This gets the lookup for the attribute new_phonesubjectid on the Phone Call form.
lookupItem = crmForm.all.new_phonesubjectid.DataValue;

// If there is data in the field, show it in a series of alerts.
if (lookupItem[0] != null)
{
   // The text value of the lookup. Set the subject line of the Phone call to this value
  // alert(lookupItem[0].name);
      crmForm.all.subject.DataValue=lookupItem[0].name;

   // The GUID of the lookup.
   alert(lookupItem[0].id);

   // The entity type name.
   alert(lookupItem[0].typename);

}