Different Header based on landing page...one database

[forced]

using session_start() or zen_session_start() outside of the zencart.

Hi all, I asked a similar question before when I first started out, but now that I am more familiar with ZC and sessions, I want to ask again. First off, here is a link to my shop:http://www.energetixjewelry.com/shop

We do fund raisers with different charities, lets say, for example, and Autism charity. A certain amount of the proceeds go to the charity. So we would advertise the domain of: http://www.energetixjewelry.com/aut From there I would like to store a session variable that will remain after the page is forwarded to the shop url.http://www.energetixjewelry.com/shop

what I have now is an index page in the /aut/ directory. on the page I have:

if (!isset($_SESSION)) {
session_start(); // This connects to the existing session 
session_register ("landing"); // Create a session variable called name 
$_SESSION['landing'] = 'aut'; 

then i use a php header location to redirect to the main shop url. now my problem is calling that variable on the main page. I want to be able to switch the header image based on what page the user first entered at.

Any ideas?