I'm running SAGE 100 v2018 and have been asked t ocreate a VI Import job where the source file contains a field that is not an invoice number but can be used to identify if the record should be grouped into an invoice (they call it CustPONo).  I'm sure there is a better way to explain it but I'm struggling with the correct terminology so I mocked up an example below.  

Example source file:

CustPONo Inv. Date      Div    Cust #       Ship   Whs   Item               Desc.                                    (Item detail information (qty price extension...)

1455248,   07022021,   02,   GPM0010,  4641,  000,  /FUEL,           Fuel Surcharge,,                  263.2,.265,69.75,Comment (Premium 93 Branded Ethanol 10.0%,,

1455248,   07022021,   02,   GPM0010,  4641,  000,  /FREIGHT-3, Freight - 3rd Party Hauler,,   9000,.0263,236.88,Unleaded 87 Branded Ethanol 10.0%,,

1455248,   07022021,   02,   GPM0010,  4641,  000,  /FREIGHT-3, Freight - 3rd Party Hauler,,   1000,.0263,26.32,Premium 93 Branded Ethanol 10.0%,,

4528634,   07022021,   02,   SMI0335,    0001,  010,  /FUEL,           Fuel Surcharge,,

The first three records would go onto one invoice while the fourth record would go onto a different invoice.  What they want to do is have the system auto-generate the next invoice number rather than use the CustPONo as the invoice number.  If the next invoice number is 1234567, the import job would bring in two invoices where the first invoice is 1234567 and contain the first three lines of information.  The second invoice would be 1234568 and contain just one line item.

I just don't know how to use the CustPONo as the grouping for an invoice then use the "Next" invoice number to populate the records based on the CustPONo grouping.

Thank you