I'm trying to do much the same thing and i must be missing something.
I'm not using quite the same tables, but their relationship is the same.. Inside the data:MAINTABLEdatasource tag, I make a data:MAINTABLEproperty tag, and its' intellisense provides suggestions.. i choose the one that is literally the name of the lookup table i want (KEYTABLE), in the above scenario, "OrderStatusType".
but i still fail to get the logic behind the proper construction of the asp:BoundField tag within the gridview's columns. how does one arrive at "OrderStatusTypeIdSource.OrderStatusDescription"? I don't see where the "IDsource" part comes from, nor does just playing around with this seem seem to be getting me anywhere.
doing the reverse works fine. within a datasource-deeploadproperties tag for the KEYTABLE is provided a MAINTABLEdatasource, and i can reference that to a subdatagrid's datasource with ease. I'm at a loss for how to use this nondatasource deeploadproperty provided by my maintable.