File content converision -Header data in Target

Here is my input file structure . I need to split each record as a message for each suplierno,ponumber
and receiptdetails

File structure

SupplierNo -1st record
PONumber
Receiptdetails 
SupplierNo - 2nd message

PONumber
Receiptdetails
PONumber     -3rd message
Receiptdetails

Content conversion record structure

BatchHeader,1,Supplier,1,POHeader ,*,ReceiptDetail,*

For the single PO it is working fine. But if the supplier has more than one PO ,
in this 2nd PO message I am not getting the  supplier no in the header . How can I  get this supplier no in the second message.on target  Or how can I add in the target side mapping to get the previous supplier no for the 2nd message

I am mapping supplierno > vendor in the top control section

Thanks for your help