When doing mass update of Carrier on shipment,it should change rate offering and rate record

Summary:

When doing mass update of Carrier on shipment ,it should change rate offering and rate record- Tried writing the agent where i am doing service provider fixed , then making rate offering and rate record as null and then assigning the rate but the problem here is that when we are taking the invalid service provider in doing mass update then it leave the rate offering and rate record as blank on shipment . So how we should tackle that if we do mass update of invalid SP then it should assign the rate offering and rate record with the