Guidance over a Twitter API project

[Edie Dias]

Hello,

I`m Edie and I am a Webdesigner.
Here is the thing. I was asked to do a freelancer with some twitter
interactions. The client has a website and wanted to do a promotion.

What is suppose to do?
The user follows the twitter sites owner. After the following action,
automatically sends to the user an e-mail with a form. But the form is
just open for the user who follow the twitter.

What I need is guidance to where to start and if is actually possible
to do this with twitter API or other method.

Thank You in advance

Edie