PO Update APIs po_change_api1_s.update_po

It is quite often to update some of the lines of a PO after it is approved.
In order to Update a PO, we can use the API po_change_api1_s.update_po.

It Update a standard purchase order or release changes of quantity, price, promise date and Need-by-date.This Need-by-date updation with this API has been enhanced in R12 only. In earlier releases updating the PO line’s Need-by-date is not available.

Psudo code of the usage
l_result := po_change_api1_s.update_po
(x_po_number => p_po_num ,
x_release_number => NULL ,
x_revision_number => l_revision_no,
x_line_number => lines_rec.line_num,
x_shipment_number => lines_rec.shipment_num,
new_quantity => NULL,
new_price => NULL,
new_promised_date => NULL ,
new_need_by_date => TO_DATE(nedbydate,'DD-MON-RRRR'),
launch_approvals_flag => 'N' ,
update_source => NULL,
VERSION => '1.0',
x_api_errors => l_api_errors,
p_buyer_name => Lines_rec.agent_name,
p_secondary_quantity => NULL,
p_preferred_grade => NULL,
p_org_id => g_org_id);

It will either return a 1 for successful update or 0 for failure.

Pre-requisites to use this API
1) PO header to be either in APPROVED or REQUIRES REAPPROVAL status.
2) No update if the revision number doesn't match the current revision.
Post Update
1)Upon successful updation,the PO revision will be incremented.
2) if launch_approvals_flag is set to 'Y' then it will launch the PO Approval. But if you set this parameter as 'Y' then the program try to submit the PO Approval for every successful update of the line.Most of the time this Approval will not update the PO to APPROVED, it may be delay waiting for some other input, so it will make the PO status as INPROCESS.
So please avoid to launch the Po Approval with this Update PO API.
3)The authorization status of the PO will be in REQUIRES REAPPROVAL is the above paramter is set to 'N'

Difficulties faced:
1) This will update the PO if it have one line without any issue in the first run.
2) If the PO have more than one line, then we need to run the Update program the no.of lines po have.We need to pass the Po line num for every run.
3)If the first PO line got updated then revision will gets chnaged to next highest number.So we need to grab the revision number for every updated line and need to input to the above program.
4) By doing this we can avoid the weird error 'The revision number doesn't match the current revision'.
5)Need to launch the PO approval manually because it will leave teh PO in REQUIRES REAPPROVAL state.