SELECT CASE $[OINV.U_UDF]
WHEN 'Cash' THEN (SELECT U_Cash FROM OCRD WHERE CardCode = $[OINV.CardCode])
WHEN 'Credit' THEN (SELECT U_Credit FROM OCRD WHERE CardCode = $[OINV.CardCode])
END
SELECT CASE $[OINV.U_UDF]
WHEN 'Cash' THEN (SELECT U_Cash FROM OCRD WHERE CardCode = $[OINV.CardCode])
WHEN 'Credit' THEN (SELECT U_Credit FROM OCRD WHERE CardCode = $[OINV.CardCode])
END