Costing of Raw material without effecting the costing of Finished Good

Dear Experts,

There is a scenario in my current client:

We need to run Cost estimates for some particulars Raw Material also.

But changes in cost of this RM, should not impact the Finished Goods cost which have been produced by using this RM.

Also we need the report of Price comparision between previous & current for this RM.

Is there any process available in Standard SAP?

Please suggest......!!!!

Regards,

Hitesh