contact form extension database on a required field

Hello, I need help in connecting a database to a required field on a contact form that i am using with Themeforest (Mestro Animated theme) that downloaded into WordPress. I will be using the contact7 form I uploaded in wordpress or I can use the form that comes with the theme. In either case, one of my required fields need to query a database in order to pass validation on that required field. The database will consist of building names. We have about 75 building names;these are our current clients. The list will be modified from time to time, therefore, it needs to be accessible for wordpress admin users to add, delete or edit a building name as they please. We would also like for the fields to auto populate when editing the database (adding, modifying). For example, if I add this building address to the database 11478 Grant Street today. Then tomorrow if I add 11478.....Hope street. It should cache 111478 or auto populate those numbers as I type; i guess kind of like what your typical browser would do when you typing in a URL and it remembers your browsing history, so therefore it auto populates what it thinks you are trying to type or search for. The enduser must provide their building name in that field. If their building name does not match one of the building names in the database, then the valdiation should fail. Otherwise, it should pass and allow the user to enter another page/or redirect to another page listing the coupons and deals for our clients. So, I need to know how to setup the database first...like where do i go to set that up and how to set it up with the building names, how do i link it somehow to the contact form and setup the pass/fail validation on one of the fields on that form. How do I do that on this form? Or is there a plugin that does all of this for me( the database, the required field, the database extension), etc. Another option, can I use a membership plug in to do this? I am thinking maybe setup a login page for those clients to login and if they enter the correct login, it will redirect them to a page that has all of the deals and coupons for our clients. I dont want to restrict the whole website because it is also designed for the public as well.