special order drop shipment on same Sales Order

I have a drop shipment and special order on the same sales order.

The special order generated a purchase order with no problems using requisition worksheet, 

and so did the drop shipment. I did each sales line individually.

However, I need to enter a different delivery address on the drop shipment PO and can't seem

to get it to work.

I'd appreciate any assistance/advice on this one.