How to group Requisition Import by Sales Order when source = CTO

The note to buyer field indicates which sales order the requisition is being created for. However, if I have several orders in the batch, the value in the note to buyer field may point to a different order#. How can I make requisition import group by sales order number so each sales order is only linked to 1 requisition. I want a 1:1 relationship between sales order to requisition. So the interface_source_line_id is always pointing back to the original sales order for that requisition.