Custom wordpress directory filter private

We have a Wordpress website which includes the Formidable plug in which we're using to build a directory of businesses. We want to include a filter to display results from the directory which you can see here... [login to view URL] The two fields at the top of the map should filter the results on the page when clicked. These fields are currently manually created so we need a developer to write the php to populate these two fields and then add the javascript to make them filter the results when they're selected. We would like the two fields to work in the same way that the work on this page... [login to view URL] Where the sub category field only shows when the category field is selected and it is filtered to only show the relevant sub categories.