Questions Copy user field from parent order

I am trying to generate a GI on the AMPRODITEM table. I have a custom field called JobNbr. I want to create a gi that will show the parent(Product) JobNbr associated with the child orders. (hope that makes sense). 

The data would be something like this

ChildOrder Nbr | ChildJobNbr | ProductOrderNbr | ProductOrderJobNbr

000000011                              000000001                Job1234

The product order number is on the child orders so the first three columns are easy. I am just stuck on how do I get a field from another order for the Product Job Nbr.