Send mail to Message Processor in Service Desk

Hello

I am trying to create a action that will send mail to message processor when he is assigned to the support message.

The problem is that when a support message is created the filed of the message processor is empty and the action can't be preformed even after I am assigning a message processor the action isn't working.

Is anyone knows what kind of condition I need to had to my action so the action will be active only after I will assign a message processor.

Thanks a lot

Lior Grinberg