Oracle forms passing parameters to a ‘DEFAULT_WHERE’ clause

SET_BLOCK_PROPERTY('XXPO_APP_ITEM_DETAILS', DEFAULT_WHERE,
                   'ITEM_ID = NVL('||''''||:XXPO_APP_ITEM_DETAILS.ITEM_ID||''''||',ITEM_ID)
And  ORG_ID   in (
SELECT
org.organization_id
FROM
hr_all_organization_units org,
per_org_structure_elements pose
WHERE 1=1
AND org.organization_id = pose.organization_id_child
AND pose.org_structure_version_id = 2061
START WITH
pose.organization_id_parent = NVL('||''''||:XXPO_APP_ITEM_DETAILS.ORG_ID||''''||',ITEM_ID)
CONNECT BY PRIOR
pose.organization_id_child = pose.organization_id_parent)
And SCHEME    = NVL('||''''||:XXPO_APP_ITEM_DETAILS.SCHEME||''''||',ITEM_ID)  ');
GO_BLOCK('XXPO_APP_ITEM_DETAILS');
EXECUTE_QUERY;