Hmm. I don't think a regular scenario will help you very much. Please have a look at the following links for more information about material flows between Profit Centers and their financial impact.
Goods Movements Between Profit Centers - Profit Center Accounting (EC-PCA) - SAP Library
Example: Stock Transfers - Profit Center Accounting (EC-PCA) - SAP Library
Also I know there should be a scenario for stock transfers between separate SAP systems. This scenario uses purchase documents in one system and automatically creates sales orders in the other (with Reference). My guess is that it uses Idocs for this. Maybe you can have a look at that scenario and use it for your problem.
Regards,
Sjaak