Hey Moira, you say your UDT has one field, but really it has to have two, right? One will be the index of the UDT and another would be the data. I just created a UDT in SO, then added a UDF in SO_SalesOderDetail and referenced that UDT on the Validation Tab. Then when I go into Sales Order Lines I do see the ALE Lookup after adding it to the secondary grid. Yours should work like that.