Insert Values Into A Nested Table?

Insert values into a table. The table is called PurchaseOrder_objtab. Here is the type for the table:

CREATE TYPE PurchaseOrder_objtyp AUTHID CURRENT_USER AS OBJECT
(
PONo NUMBER,
CUST_ref REF Customer_objtyp,
OrderDate DATE,
ShipDate DATE,

[code]...

The LineItemList_ntab is a nested table.

Here is the create code for LineItemList_ntabtyp:

CREATE TYPE LineItem_objtyp AS OBJECT (
LineItemNo NUMBER,
Stock_ref REF StockItem_objtyp,
Quantity NUMBER,
Discount NUMBER
)

[code]...

In the above code, the LineItemList_ntab is an empty LineItemList_ntabtyp. I am wanting to add values to this nested table rather than it being empty in the INSERT INTO code.

Here is some of the code I have tried to insert values with:

INSERT INTO PurchaseOrder_objtab
SELECT 1008, REF(C),
SYSDATE, '12-MAY-1999',
LineItemList_ntabtyp(1, REF(StckItem), 10, 1) FROM Stock_objtab StckItem WHERE StckItem.StockNo = 1004,
NULL

[code]...

The first insert statement above produces the following error:

SQL Error: ORA-00933: SQL command not properly ended

The second insert statement above produces the following error:

SQL Error: ORA-00936: missing expression

successfully insert values into the LineItemList_ntab nested table?