Hi Madanraj,
You can possibly do this in two ways. I have not tried but it should work.
Options:
(1) Use of Service Types for the workflow task - you will need to create a service type with repeat events and send out notification to the task assignee periodically if the task is pending (create condition to check these). If the task assignee is blank, no one gets notified. When you populate the task assignee, on next periodic evaluation, the task assignee will be notified. I personally do not like this approach as I have a fear that it may overload the system if you have too many such repeat events. Do not know regarding the volume of tickets in your case. In your case this may be appropriate as you are looking for repeat events. Keep the repeat interval as high as allowable.
(2) Use Activity Notification - when an assignee of a task is updated, it triggers the Transfer Activity. Create an event for the Change Order WF task and put in an action to send out multiple notification to task assignee with the condition suitable for that WF task. The condition can be tricky based on what you would like to do. If the task assignee is empty no notification should go out. I have not tried this method but it is worth giving a try. Worst case you can split out the task assignee association from the "Transfer" activity and create a fresh new activity notification called "Task Transfer" and associate the 'task assignee' field to this activity. Then on any change of a task assignee it will trigger this "Task Transfer" activity and try notification in the same manner explained above.
As always, custom code can easily do this, but definitely do not recommend custom code. Configuration is the way to go.
Hope this helps. Good luck.
Indrajit Banerjee.