ePro Approval Workflow for Dept ID

Business requirements are to route requisition approval via Dept ID with approval limits.  However, there is only one Manager per DeptID (in the chartfield set-up) so if the requisition is greater than the amount the department manager is authorized to approve for, the system returns an AWE error.  Is anyone else using Dept ID as an approval step.  Is there a way to set-up requisition approval hierarchy by tree?  Are there any options for this kind of set-up?  The business does NOT want to use fiscal approval (by Supervisor ID) - ONLY Dept ID Manager Approval.

Thank you!