How to create a business rule to change the status of a request

How to create a business rule to change the status of a request

I currently have business rules setting the group and status of new ( incoming) requests.  I would like to create a business rule that would set the status of a request to "assigned" when a technician is assigned the request and at the same time when as is the the case for PM requests the tech is already assigned the request should go to the assigned level vs the pending assignment status for new requests

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