Hi Gopi,
Create a program in your application server and assign a tcode for that, call that tcode once the file has been uploaded in cg3z, and keep your logics there and create PR through below BAPI.
Use BAPI_REQUISTION_CREATE
call function 'BAPI_REQUISITION_CREATE'
exporting
skip_items_with_error = 'X'
importing
number = h_banfn
tables
requisition_items = req_item
requisition_account_assignment = req_acct
requisition_item_text = req_text
return = return
exceptions
others = 0.
Other related Bapis for purchase requisition are BAPI_REQUISITION_GETDETAIL and BAPI_REQUISTION_CHANGE.
Regards,
Venkat