Hi Kellen,
Does your f_OrderDtl table have any location identifier that can be mapped to your regions or territories? You may need to create a location cross reference.
We use an Epicor ERP product call Eclipse. Not sure how similar or different it is to your system, but we have several levels we like to aggregate to, including region. To do this, we created a cross reference in Excel that maps all our location levels into a simple hierarchy - in our case, we have individual branch locations (lowest level) that roll up to markets, and markets roll up to regions. The hierarchy is setup as a dimension and we map our streams to that dimension when the location is relevant.