Program to create PO from PR

Hi Experts

I am new to ABAP. My requirement is create PO from a released PR.

I am able to create a PO when i open ME21N and provide requisition number in ITEMS tab, save.

But now i need to create a program in SE38.

when i m trying to use bapi_po_create1, i m getting errors : maintain services or limits .

can you please send me pseudo code to achieve this .

Thanks in advance.

Regards

Abhishek