I want to create a trigger toupdate PROMISED_DATE on a PO once is been approved , promissed date =

This is a business need,  becases we print the promised date on the PO, we cannot calculated in advance the promised date on the PO  before the PO has been approved, because we only  send approved PO to suppliers and the approval of the PO can take some time if enters into the approval workflow.

trigger :

REATE OR REPLACE TRIGGER XXFIN_PO_LINE_LOC_PROM_DATE 

BEFORE INSERT OR UPDATE ON "PO"."PO_LINE_LOCATIONS_ALL#" 

FOR EACH ROW

DECLARE

v_mexico_flag number;

BEGIN

             select count(*)  

             into v_mexico_flag

             from hr_operating_units 

             where 1=1

             and organization_id=:new.org_id