As of 9.1 M050 the class file is distributed with Windchill. Prior to that you'll need to put the class file that Marc has attached to the previous post.
Mike here is the presentation with the rework expressions on page 36. This is all implemented in a production environment for PDM 9.0 M060. I have tested at PDM 9.1 with slight modifications at PDM 9.1 M040. Just installed new development server at 9.1 M060 and will sooner or later get around to testing and fully configuring for that version.
Marc, does this allow the requester to automatically gather all of the previous objects after rework, or do they have to manually re-gather objects?