Can I adjust value of specific inventory items?

I doubt this is possible, but am curious from any Inventory Mgmt czars out there.

We utilize a process where we manage evals using a sales order (we separate them from real orders by using a custom field that identifies it as an eval). The revenue impact is always $0 however when we fulfill, CoGS account gets debited and the asset account gets credited. The process pulls initially from "new" inventory (we call Location:'Main'). When the eval is completed and no purchase is made, we process a return authorization, receive the return of items and put it back into a different "used" location (we call Location:'Sales').