Update PO in DMS Object Links

Dear all,

I have created a function module(ZDMS_DOC_UPLOAD)  for attaching the documents  to Cv01n transaction its working fine.

i'm using two standard  FM 1. BAPI_DOCUMENT_CREATE2 

                                        2. BAPI_DOCUMENT_CHECKIN2

Here my inputs are document type , document part , document version  and the document file ( this file is updating the CV01N transaction ).

My requirement is i want to enter the PO number also as a input to the ZDMS_DOC_UPLOAD and thisPO number  have to automatically attach to the Purchase Document field of  OBJECT LINK Tab  in CV01N transaction.

I want to know is there any function module or BAPI available , that will automatically attach the PO number to the  Purchase Document field of

OBJECT LINK  TAB of CV01N transaction.

I need your help...

thanks

Nidhi....