Sub-contracting scenario

Hi

Our client uses around 20 to 25 sub-contractors to make finished products.

Raw materials are sent by vendor directly to sub-contractor and sub-contractor dispatches finished goods to the WSP (Whole sale stocking point).

Client HO (head office) pays the conversion cost to sub-contractor.

The lead time of production in sub-contractor location is around 15 days. In the 15 days suppose after 7 days if they produced some qty. of FG and sent it to WSP. So physically raw material is consumed and in the system we are not able to identify the goods consumption if we go for sub-contracting PO.

How to map this scenario? How we can able to see the material consumption. Tell me the steps in detail. If anybody have the document of this pls.