Approval Workflow

Hi All,

Can some one please assist me on the below.

Scenario: Currently we have existing IT shop and a work flow is assigned to it. Now the request is we are creating to new workflow for the same IT shop.

So the question is if there are products already requested from this IT shop and are in pending state should follow the old workflow and the new requests that will be created should follow the new workflow.

Can some one assist as if there is any config parameter or any other way from which we can achieve this .