Not More Then 5000 in purchase order amount - personalization

Form personalization

Trigger : WHEN-VALIDATE-RECORD
Trigger object : PO_LINES

CONDITION
:PO_HEADERS.PO_TOTAL_DSP>5000 AND :PO_LINES.PO_LINE_ID  IN (SELECT PO_LINE_ID FROM PO_DISTRIBUTIONS_ALL WHERE REQ_DISTRIBUTION_ID IS NULL)

message : amount is more your credit limit -----Error