Hi Anand,
I think what you want to do is sending message between different branches of process instance. If ADMIN have not assign the task to a employee, the starter of process instance could have a chance to end the process instance. But if ADMIN is already assign the task to a emloyee, the starter of process instance could not cancel the process instance any more. Do you mean that?
Actually there is no way to send message from a branch of process instance to another one. If you use my process sample showing above, No matter what the ADMIN do, the starter could always terminal the whole process instance.
I think you should find a way to create a task to the starter dynamicly and listening the ADMIN's assigning behaviour, if ADMIN already assign the task to other person, you have delete the starter's task.