Hi Nikki,
You can acheive this by using special procurement key.
1) Create special procurement key and give sender & receiver plant combination in it(sender - XY0000 plant and receiver - AB0000 plant)
2) Assign special procuremnet key for material AB0000 in costing 1 tab.
You need to have a valid cost estimate for XY* material before running the cost estimate for AB* material.
Regards
Bhaskar