Update old workflow instance with the newly transported workflow

Hi ,

We have made some changes in workflow in development system and upon testing sent the same to quality system.

While testing , we found that the whatever NEW WF we have created are working fine (as per requirement) , but the request created before this transport are behaving the same way as with old versions, I think this is due to the reason that , system is still using the old workflow defination for the old cases.

Now my question is , how can I update these old workflow instances with the newly sent workflow ??

Please help.

Thanks.

Ekam