How to End Date a Previous Cost scenario

Summary:

End Date a Cost Scenario, to avoid cost being considered from Previous cost scenario for a WO

Content (required):

We have created a new Cost Scenario for Process manufacturing , which has Finished goods (main product Output) and By-Product. In the new cost scenario, cost for By-product was changed. However, Work Order (which was created after the new Cost scenario was published) still considers the old cost for the By-Product from previous cost scenario. And the difference between the new and old cost, is shown under Variance.

Could anyone please let us know how to End Date a Cost scenario? so that System does not consider the cost from Previous ones.