I'm working on a ss2.0 script and having trouble with a search. The search is being made against inventory items. I'd like to include a column from a related record. Normally that wouldn't be an issue. But in this case, the related record also happens to be a custom record type. The ID for the custom record type is "customrecord_test_itemprogram" and the ID of the field that I'm trying to include is "custrecord_test_external_uid." So the full column that I'm specifying is: customrecord_test_itemprogram.custrecord_test_external_uid Here's the code...

var itemSearch = search.create (
	{
		type: record.Type.INVENTORY_ITEM,
		filters: 
			[
				['parent', <http://search.Operator.IS|search.Operator.IS>, internalID]
			],
		columns: 
			[
				'itemid', 
				'displayname',
				'quantityavailable',
				'customrecord_test_itemprogram.custrecord_test_external_uid'
			]
	}
);

The error message that I'm getting is: "An nlobjSearchColumn contains an invalid column join ID, or is not in proper syntax: custrecord_test_external_uid." Am I trying to do something that just isn't possible (joining to a related custom record)? Or is the syntax that I'm using incorrect?