We have many invoices were we are not able to book additional costs against a material number by a PO in Medius XI against our ERP system(SAP)

Example:
1.We purchase a raw material from a vendor. This invoice is booked against a PO with a Goods reicept in our ERP system(SAP), which is connected against a material number.

1. Then we receive an additional invoice for freight costs from a 2nd vendor. This invoice should then be booked as a "subsequent debit" against the same PO against the same material under step 1. The additional cost must be visible in our material master regarding the totale value of the raw material with all the extra variable costs. In addition to freight costs, the same shipment also creates other costs like terminal charge from a 3rd vendor, other fees from a 4th vendor etc. The only way we are able to book invoices against the material is through t code MIRO in SAP.This is very time consuming!