How to exclude mandatory attribute(PO Number) when customer is having a custom grouping rule created

Hi Team,

When creating the invoices via the Auto Invoice program the standard functionality is to group the invoice by Customer PO number. However the requirement is to group the Invoice lines based on the Bill of Lading (created a custom grouping rule) by disregarding customer PO number. So that one Invoice is created based on the Bill of Lading containing multiple sales orders with multiple lines having multiple PO numbers.

Thanks in Advance and Happy New Year.

Regards,

Prakash