Sub-contracting Issue

Hi experts

I have an issue related to sub-contracting.

Component 'A' is used to make materials B,C and D(at subcontractors end)

I have made a sub-contracting PO for material B and did transfer posting. I have consumed 50 % of the quantity of 'A' and made B material.

Now i want to make material 'C' by using the remaining component of 'A' at the sub-contractor's end.

How can i receive the material 'C' from sub-contractor because already i made sub-contracting PO for the material 'B' and sent the component 'A'.

Please suggest me a solution for this scenario.

Thanks & Regards

Bala