How to merge two division sales order 2 single invoice

Dear All,

We have a scenario as below

Sold to party /Payer are same

Ship to party - Different

Creating Seperate sales order for  2 division materials as the material are manufactured by diffferent plant and delivered seperately.

But the invoice to be generated single as depot accepts only single  invoice per company code.

When executing two sales orders for  proforma invoice system splitting the invoice due to different hearder data(i .e division ,plant,incoterms)

When generating commercial invoice for all the  delivery in two divisions(under one sold to party) system splitting the invoice due to diffferent header data(i .e division ,plant,incoterms)

Pls explain how to merge the division to single invoice.

Thanks & Regards,

Kumarbabu.