Hi Shobak - If I have understood your question correctly - you want the approval on Sales order to be granted automatically once the SO is sent for approval, w/o any user pressing "Approved" on the other end.
If you want to automate sales order approval, I'd rather suggest disabling the workflow altogether. Automatic approval of an order, without any human intervention is counter-intuitive to the while approval process design. The approval workflow is designed in such a manner that a user sends the document for approval and it is reviewed & approved by a higher level user
