Hi Ravi,
I don't need to handle my workflow as for PO(according to existing requirements) WF does not get triggered for PO Creation, it only gets triggered for PO change. 
Lucky me
While i am creating a PO using BAPI_POEC_CREATE FM as per following thread:
Upload PO data into SRM system from flat file
I am getting few errors:
Enter exactly one partner of type Supplier
Supplier 0020000000 not intended for purch. org.
Partner of type Supplier is not authorized for this document; check entry,
However with the same data i have few POs created when these were created from a SC via Portal.
Any idea what is causing this error?
Regards,
Ashish