You cannot change State in response to change in other field's value - the OM and work item type definition have no support for that. You would have to write your own app to do that.
Actions were added for the integration with the version control; right now the only action recognizeable by the system is Microsoft.VSTS.Actions.Checkin. You may define your own actions, but they will have no effect on system's behavior. However, you could use them in your application to determine the state the action should bring your item to (WorkItem.GetNextState, WorkItemType.GetNextState). Therefore I don't think you could use actions to achieve your goal.
Thanks,
Alex |