Personalize Form sort order using non-database table field

I'm trying to sort the Physical Inventory Tag counts screen via forms personalization.  Since two of the fields that I want to sort on are non-data base fields, I need to use a select statement in the order by property that I am personalizing.  I am using the following:  subinventory, (select segment1 || segment2 || segment3 || segment4 from mtl_item_locations mil where mil.inventory_location_id = locator_id and mil.organization_id = 109 and locator_id is not null), (select msi.segment1  from mtl_system_items_b msi where msi.inventory_item_id = inventory_item_id and msi.organization_id = 113 and rownum = 1),tag_number    My question is, how can I reference a field