J-BusinessDirectory - Separate sub-category search field in the "JBusinessDirectory Search" module?

I'd like to customize the "JBusinessDirectory Search" module this way: When users chooses Category in the first field, to see second drop down with the sub-categories from the chosen category.
I have to do this because i have over 70 categories, so the first drop down is way too large and not user friendly. Can anyone here let me know how can i achieve this? 

Hi,

You can activate the autocomplete feature and make the categories searchable.