Check out the ChangeService2 API (in wt.change2 package) which has methods to support your use case. ChangeService2 methods can be called by ChangeHelper2.service.anyMethod(). Methods of interest are most likely getChangeablesBefore() to get Affected Objects and getChangeablesAfter() to get Resulting Objects. Note - I've left out the parameters for simplicity so refer to the JavaDoc.
