Update Shipment_stop refnum once Service Provider adds Shipment refnum from SERVPROV

Hi

We have a business requirement to update shipment stop refnum once service provider updates the shipment refnum on the shipment from servprov domain.

I tried with shipment modified event of the agent from planning domain but this did not worked.

Please let me know how we can achieve this requirement or which event we can use to update the shipment stop refnum from shipment refnum ?

Thanks!

Regards
Vijay Agrawal