Copy refnum from shipment ship unit to shipment

Summary:

I try to cpy the shipment ship unit refnum to my shipment but is not working. I'm using the standar agent to make the copy with a modified action but is not taking the action. I don't know if the standard action working or I need to create the SQL agent.

insert into shipment_refnum (
SHIPMENT_GID,
SHIPMENT_REFNUM_QUAL_GID,
SHIPMENT_REFNUM_VALUE,
DOMAIN_NAME
)
select
'$GID',
'DOMAIN.TRAILER NUMBER',
REFNUM_VALUE,
'DOMAIN'
from (
select REFNUM_VALUE
from s_ship_unit_refnum
where S_SHIP_UNIT_GID in (
select S_SHIP_UNIT_GID
from shipment_stop_d