TAble type value set to refer field in the screen

In table type value set how to refer field from screen eg (po_header_id)

Content (please ensure you mask any confidential information):

Dear Team,

iRequirement

In PO screen i have created DFF with Table type

query

SELECT DISTINCT PRHA.requisition_header_id

FROM por_req_distributions_all PRDA,

por_requisition_lines_all PRLA,

por_requisition_headers_all PRHA,

po_headers_all poh,

po_distributions_all pda

WHERE PRDA.distribution_id = req_distribution_id

AND PRDA.requisition_line_id = PRLA.requisition_line_id

AND prha.requisition_header_id = prla.requisition_header_id

and poh.po_header_id=pda.po_header_id