NOTE: for use with Shipping Estimator and Guests etc. ... a better choice on obtaining the subtotal of the cart for the calculation is:
$_SESSION['cart']->show_total()

Something along the lines of:
Code:
global $cart;
echo 'Handling: ' . 'subtotal: ' . $_SESSION['cart']->show_total() . ' ' . constant('MODULE_SHIPPING_ZONES_HANDLING_' . $dest_zone) * $_SESSION['cart']->show_total() . ' = ' . (strstr(constant('MODULE_SHIPPING_ZONES_HANDLING_' . $dest_zone), '%') ? constant('MODULE_SHIPPING_ZONES_HANDLING_' . $dest_zone) /100 * $_SESSION['cart']->show_total() : constant('MODULE_SHIPPING_ZONES_HANDLING_' . $dest_zone)) . '<br>';
Then change the current calculations of the handling fee to use the calculation included in that echo:
Code:
(strstr(constant('MODULE_SHIPPING_ZONES_HANDLING_' . $dest_zone), '%') ? constant('MODULE_SHIPPING_ZONES_HANDLING_' . $dest_zone) /100 * $_SESSION['cart']->show_total() : constant('MODULE_SHIPPING_ZONES_HANDLING_' . $dest_zone))
This would allow you to change the Handling from 10% to 7.00 on a per Zone basis ... without having to do a lot of extra work ...