Restrict the items entered from one child table into another

Hi,

I have a unique situation, I think. I have a Delivery Note page, where I have 2 child tables. One is for the Delivery Note Items and another is for the Packing Details. Our requirement is that whatever items are there in the Delivery Note Items, only those should be displayed for selection in the Packing Details child table. Is there an option for that? So, if there are 3 items in the Delivery Note Items, only those 3 items should be allowed for selection in the Packing details table.

Thanks
Uma