Conditional Value List based on multiple fields - in find mode

I've set up a database for my organization that can take our total client file (about 20,000 records), drill it down using finds to a targeted list, and export that to a spreadsheet. Easy enough.

I would like to have the value lists of several fields dynamically update in find mode. For example, if I had the following geographic fields:

State

County

Town

Zip

Region (we've already defined this)

If I select state and region in find mode, I'd like for the drop down lists for counties, towns and zips to only include those values that are in the correct state and region. Basically, I want the current value lists for any of these geographic fields to reflect the most up to date constraints based off of the selected queries in find mode.

All of the information is in one table, and I don't see any easy way to split it into several tables. Can someone help me out on how to do this using a self-join relationship?

I haven't been able to get conditional value lists to work at all, even on the most basic level, so a step by step guide with specific instructions would be incredibly helpful. Thanks!