How to customize orders total calculations

[catv]

I'm using the master password contrib, as part of my effort to use the front end of the site for our 3dparty sales and offline sales. I want the master password admin to be able to change the order total in the checkout process by making the order's total to be able to be edited via a form input. I have this working for the shipping total, by manipulating the Session variable for shipping cost. Now I'm stuck trying to fitgure out where the total is being calculated, so I can simply subtract an amount by a percentage. so I can do something like Session[Ordertotal]-Session[mypercentage].

I'm looking through the files, but the orders total looks to be so abstracted in code I 'm just chasing my tail on this one.

I'm looking in all the right files I think, but kind find where I can code in a simple substraction off the total, We're only using the flat_flat shipping right now.

I see this in tpl_orders_module_orders.php
I don't understand what the heck this array is suppose to be?

echo $GLOBALS[$class]->output[$i]['text'] 

I see some intresting stuff in
classes/orders_total.php but everthing is too abstracted to make sense of it.

Where on earth is the Session etc. variable that is holding the order's total that I can manipulate???

Thanks in advance...

[catv]

I found this file too

modules/ot_total.php

Just found something in this file.

by chaning this line

'text' => $currencies->format($order->info['total'], true, 

to this

'text' => $currencies->format($order->info['total']-5, true, 

I'm able to subtract $5 off the total, I think I found my variable I was looking for.

Is there a better place to code this in? and can I override this file or not?

Now I'll post my value to a session variable and have it change the order's total, and re-assign the value to the new value, right?

[catv]

I have it working partially put it doesn't calculate exactly right, any idea?



includes/modules/order_total.php

    function process() {

    
      global $order, $currencies;
      $this->output[] = array('title' => $this->title . ':',
                              'text' => $currencies->format( ($order->info['total'])-($order->info['total'] * $_SESSION['orderDiscount'])  , true, $order->info['currency'], $order->info['currency_value']),
                              'value' => ($order->info['total'])-($order->info['total'] * $_SESSION['orderDiscount'])  );
    }