Visitor Must Submit Info To View Page | Recommendation and Advice?

[noxbane]

So I have a client with a Website A who has a property search on Website B.

Whenever someone on Website A clicks on the Property Search button, before they are redirected to Website B, I want to present them with a form to grab some basic information. After they fill it out successfully, they will be redirected to Website B. If they have already filled out the form once before, they can enter their email (or some unique identifier) to bypass filling out the form again.

The people won't be "users" of the site, we are just trying to grab their info in order to generate a lead. They don't need to be registered as a Wordpress user or anything, just have their info stored in a table. The only functionality they will ever use is just being able to click on the Search Properties button and bypass the form if they have already filled it out before.

Now this is pretty simple if I was just writing it all myself with PHP. I'd just make a form, store the submitted info in a table and then when they came back a second time, just check the table for their email address.

But since I'm using Wordpress, I had a question. I dont know how to add my custom code to a CMS like Wordpress. Do I have to create it as a plugin?

If anyone has suggestions for a better method or any sort of advice at all, I'd be grateful for it. Thanks.