So if I pick a parent thing (manufacturer) there will still be maybe 1000 sub items?
You can do it with forms if you prefer though. If you have a mix of sources (different tables/queries) that you're getting list values from then perhaps one approach would be to use a staging table (temporary data, not temporary table). Perhaps a double click event on the textbox (so that it doesn't open the list form just because you click/enter on it) and open the list form based on the query you need to populate the form. Not clear if you want to select multiple values/records or just one. If the latter, you'll have to loop over the selections. Regardless, my thinking is that you append the first selection to the temp table and update the rest of the fields as you go. I don't really see that working with multiple selections though as you'd have say 3 records. Where do you put the other selections if there are only 2?
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.