How to add a new shipment line to an existing PO line using Purchasing open interface?

Hi all,

    Is there any way to add new shipment lines to an existing PO line using PO open interface? There is a mention in 11i Open interfaces manual that we cannot update existing purchase order lines. I believe adding a new shipment line is an update to existing PO line and hence it should not be possible. However, I am working on R12, and would like to know if there is any change to this. The metalink notes explaing the changes to open interfaces do not give any such detail. Could any of you please let me know if this is