Add another sort-by field into a listings box

I've created a Listings Box that displays 1 of my categories but I need to narrow down the girls that are displayed in the box.

Can another dropdown box be added under "/admin/index.php?controller=listings_box&action=edit" that allows me to choose stateregion or postcode

I'm using Escort 4.2.0

edit: I've tried this edit by Viktor but can't get it to work by State/Region

Hello Beau,

It will be customization and I suggest you submit the ticket with your request.
Our staff will consider your request and will try to help you.

Thanks.