Master detail lookups

I have a scales entity that has a location that belongs to a customer, so  Scale.Location.Customer.  Sometimes the end users want to move one of their scales from one of their locations to another.  In my Aurelius dataset I can create a lookup field to the locations table for the users to pick from but it will show me all locations not just locations for the current customer.  

If was working with a TQuery I think I could set the TQuery's datasource property to the scales dataset as a master dataset and parametrise the detail's query with the customer id and get what I want but AureliusDatasets don't work this way. What do you suggest?

You use OnDataChange event on master datasource and on each change you reload the Locations object filtered by the customer id.

Or, if you prefer to do that at client-side, you can use OnFilterRecord event in Locations dataset and filter the locations in-memory by the customer id.