Multiple Shipping Origins For Dummies?

I'm at my whits end trying to figure out how many different times shipping cost are calculated in Zencart...3 weeks X 10 hours a day trying to figure it out - stubborn or stupid???

I have added code to the ups.php module that calculates shipping by origin and it works great on the shipping estimator and checkout shipping pages.

I though this would be a good place to put the code...assuming any time a quote is called for, it would calculate it here.

However, the shipping charges change when I go to my checkout payment, confirmation, and payment pages.

I know checkout payment is calling the ups.php page, somehow, because it is using my calculations for shipping origins...it is not using my shipping cost though.

I have tried setting the following variables equal to my program $total_shipping_xxx but these values are getting wiped out when I advance to the next page in the checkout process.

$order_totals[1]['value'] = $total_shipping_GND;
$order_totals[1]['text'] = $total_shipping_GND;
$order->info['shipping_cost'] = $total_shipping_GND;
$_SESSION['shipping']['cost'] = $total_shipping_GND;

I thought $_SESSION was a global variable that would be available to any page...however, I have noticed that the session is unset an several places.

:please:

How can I make the $_SESSION['shipping']['cost'] available to all of the pages following checkout shipping?

Can anyone tell me how shipping is calculated on the pages following checkout shipping?

I have been studying every page associated with shipping and echoed back all arrays and variables trying to trace how the shipping is calculated after the checkout shipping pages but darned it I can figure it out.

I also attempted to incorporate drop ship core 2 into my 1.5.4 cart but there has been so many changes made since 1.5.1 that it is more confusing trying to integrate than trying to write my own code for handling multiple shipping origins.

I'd appreciate any insight given to help me slay this monster.