Refer a friend sidebox

I'm hoping to create a new sidebox - I don't think this exists in the supplied Zen Cart 1.3.7.

The idea is simple:

1. It will display whenever the user is logged in
2. It will accept an email address to which an email will be sent
3. On submitting the form it will validate the email format
4. if the format is valid, it will send a standard email asking the person to try the site
5. after sending, the page where the user was will reload in the browser

So, I've achieved 1 and 2. I'm not entirely sure how or where to place the code for 3, 4 and 5.

Can anyone give me some pointers, please?

Rich

You might peek at the Free Software Add Ons ... a search for:
friend

comes up with:
http://www.zen-cart.com/index.php?main_page=product_contrib_info&products_id=1009