How to report material consumption as WIP working with cost collectors?

With costcollector WIP is calculated at the moment of confirmation.
Currently if the raw materials are already consumed on a production order, but if at month end there is not yet a confirmation on the order, the raw materials fall into consumption in the P&L. Whereas they should be in WIP.

How could we solve that these raw materials fall into WIP in stead of consumption? Backflushing could be a solution (but then we loose again the information on actual consumption) ...other possibilities?