Let's say the three manufacturers are using manufacturers_id 1, 17 and 19 ...
Code:
global $cart;
$chk_manufacturer_1 = $_SESSION['cart']->in_cart_check('manufacturers_id','1');
$chk_manufacturer_17 = $_SESSION['cart']->in_cart_check('manufacturers_id','17');
$chk_manufacturer_19 = $_SESSION['cart']->in_cart_check('manufacturers_id','19');
$extra_charges = 0.00;
if ($chk_manufacturer_1 > 0) {
$extra_charges += 3.50;
}
if ($chk_manufacturer_17 > 0) {
$extra_charges += 3.50;
}
if ($chk_manufacturer_19 > 0) {
$extra_charges += 3.50;
}
then just add the:
$extra_charges
to the cost in the function quote ...