-Personnel number is not related to vendor in my case.
-GL Accounts allow input of pernr as manual entry through MIRO does fill the fields.
-If you read the documentation on EXTENSIONIN for this BAPI, you would've found that the only structure available is IVTEXT which has very limited number of additional fields (not including pernr).
I'll try to use the GETDETAIL BAPI and report back.
Thanks