Invoicing various deliveries

Hello experts

I have a situation were we copying various deliveries onto one invoice and we losing the sales allocation.

In more detail

1. On a single BP we have various addresses(CRD1.Address)
2. Each address has a UDF called Sales Code (CRD1.U_SalesCode)
3. Each address can have a different sales code. So each delivery allocated to a different sales exec
4. We copy all the deliveries onto one invoice. This is so the customer can see all as a single invoice for the one Business Partner.
5. The invoice then takes the sales code on the default address
6. Therefore the other sales codes have no sales when looking at the OINV table.
7. We use the OINV table to look at sales per rep and therefore do this for bp's with the above scenario

Is there any alternative to this so that I can see all sales codes on one invoice the OINV table as per the deliveries