Copy control Billing to billing

The freight pricing condition is a manual condition which is being updated during Billing. I want this pricing condition to flow to the Commercial billing also which has a different billing doc type. Commercial Billing is being done for multiple billing doc-nos together. Please let me know how to achieve this. I have tried to do copy control billing to billing however one commercial inv is generated for each billing number which is enterred instead of one billing document for multiple billing documents.