How to update the price or quantity of complex purchase order using Open Interface PDOI or API in R1

Hi,

I want to update  the price or quantity of complex purchase order by customization programs in R12.1.3. I try to use PDOI or API po_change_api1_s.update_po , but fail.

The following doc is only add a line to complex PO, cannot match my requirement. Can you help me to resolve it?

How To Import Complex Purchase Orders Using the Purchase Document Open Interface PDOI (Doc ID 1367326.1)

Thanks.