Subcontracting between two plants in different company

Hi Guru!

this is my scenario:

Company A + plant A1

Company B + plant B1

I have to move, in subcontracting scenario, raw materials from A1 to B1.

The materials involved into the flow have to be (of course) valuated only for A1, but they have to be seen in stock in both of plants. I think that The Raw Materials must be seen in plant A1 like special stock 'O' and also in plant B1 like special stock 'B' (I suppose), or something similar.

At the same time, final products must be sent back to A1, with the same problem for valuation (valuated in A1 but not for B1 and stock showed in both plants).

This is a typical subcontracting flow, but unfortunately between two plants!!!

Can you help me? do you know how set this flow in SAP?

Tnx in advance,

SS