Custom PLL with GO_BLOCK

Question

Hi
please help or suggest.
I'm setting a Delivery To Location on Purchase Order Distribution Block required, so that when users a trying to save the record a message should pop up notifying then that they must populate the DELIVERY TO LOCATION address field i've used the GO_BLOCK but im getting this error frm-40737: illegal restricted procedure go_block in WHEN-VALIDATE-RECORD trigger.
Please help and see my code below.
begin
     app_item_property2.set_property ('PO_DISTRIBUTIONS.DELIVER_TO_LOCATION',required,property_true);
     if name_in('PO_DISTRIBUTIONS.DESTINATION_TYPE') = 'Inventory' then
            app_item_property2.set_property ('PO_DISTRIBUTIONS.DESTINATION_SUBINVENTORY',required,property_true);
     end if;     
     if p_event_name = 'WHEN-VALIDATE-RECORD' then
           if p_block_name = 'PO_LINES' then
               if name_in('PO_DISTRIBUTIONS.DELIVER_TO_LOCATION') is null  then
                         fnd_message.set_name('XX','XX_PO_DELIVER_TO_LOCATION');
                           fnd_message.error;                          
                           raise form_trigger_failure;
               end if; 
               if name_in('PO_DISTRIBUTIONS.DESTINATION_TYPE') = 'Inventory' and name_in('PO_DISTRIBUTIONS.DESTINATION_SUBINVENTORY') is null then
                         fnd_message.set_name('XX','XX_DESTINATION_SUBINVENTORY');
                           fnd_message.error;
                           raise form_trigger_failure;
               end if; 
       end if;
     end if;
  exception
          when FORM_TRIGGER_FAILURE then
          Go_Block('PO_DISTRIBUTIONS');
             IF NOT FORM_SUCCESS THEN
                  RAISE Form_Trigger_Failure;
             END IF;          
          when others then
          Raise;
  end;     

Answer 1

Lethu,
you cannot use navigational triggers in WVR.
Why can't you use forms personalization to achieve this?
This is way simpler than modifying the custom.pll.
HTH,