multi-selection list with populated data

[Dr.NeBoo]

I have a multi-selection list that needs be able to have selections from multiple sets of populated datawe have a database of stores separated into [Company] -> [Region] -> [District] -> [Individual stores]there are multiple stores in each district and multiple districts in each region. the companies are made out of multiple regions.having said that - I need to be able to select multiple stores (or possibly all stores) in specific districts (possibly from multiple districts or regions at the same time)I figured the easiest way for this would be serial inputs selection of the company opens all available regions in the 2nd select box selection of a region shows all districts in this region in the third box and selection of of the district will show all stores in the district in the final box.how can I allow the selection of stores from multiple districts following this setup - or do you know of a better setup.