Set Analysis with Concat

[#1]

Hello. I have a chart (straight table) with columns region, warehouse, item and quantity. I'm trying to add a new column that shows, for each item, a concatenation of all warehouses that have the item in stock (Qty > 0). I'm getting hung up in the Aggr function or set analysis. The list keeps changing when different selections are made. Can someone have a look? See attached. Thanks.

[#2]

Thanks. That only seems to work if a single item is selected.

[#3]

This works well. I'm going to adapt it to my production app and see how it performs. I'll also have to spend some time with it to wrap my head around how it's working.

Thanks for your efforts!