Need exclusion rule for Internal Req approval based on Source org/location

The out-of box Approval Group functionality bases location and account exclusions on the destination organization/location on the internal requisition. Has anyone found a way to base the exclusion on the Source organization? Client has many stores that can order from each other without approval, but some organizations are Distribution centers, and the client wants approval required when a store orders from a distribution center. Trying to avoid approval WF customization if there's a better way to solve this. Thank you!