Invoice split

Good morning,

I have an sales order where i'm salling a stock material (item category TAN) and a service (material type DIEN and item category TAD). A delivery is created with reference to order for the stock material. Then i create the billing document with reference to the delivery and the order. If i do this to a national customer i have no problem and the billing document to the material and the service is created correctly.

When i do that to an external customer i have a problem with the split in the billing document because of export indicator and number of foreign trade data.

In the copy control between the billing document and delivery i have "A - Copy export data in the delivery" in the determination of export data field. In the copy control between the billing document and sales order i don´t have nothing. However if in this field i put A like in the copy control of the delivery i resolve the split problem, but the service ask for foreign trade data and we don't want that the user need to insert foreign trade data for a service this is only necessary for materials that have delivery.

What can i do to don't have split in the billing document and at the same time don´t have to fill the foreign trade data to the service.

Can anyone help me please?

Thanks.