How to make 'Required' Fields in the Oracle Apps Custom Form EBS 12

How to make 'Required' Fields in the Oracle Apps Custom Form EBS 12

IF :XXNAG_PR_IR_FORM_BLK_V.CREATION_REQUISITION ='Y' AND
:XXNAG_PR_IR_FORM_BLK_V.REQUISITION_TYPE ='Internal' THEN
SET_ITEM_PROPERTY ('SOURCE_ORGANIZATION',REQUIRED,PROPERTY_TRUE);
ELSE
SET_ITEM_PROPERTY ('SOURCE_ORGANIZATION',REQUIRED,PROPERTY_FALSE);
END IF;