//this function is called each time the checkout button of the cart is clicked
        function googlecartOnCheckoutClick()
        {
            //get the subtotal value of items in cart
            var subtot = googlecart.getSubtotal();
           
            //get the DOM element with ID of myShipping
            var ship = document.getElementById("myShipping");
           
            switch (true)
            {
                case (subtot <= 4.75):
                    ship.value = 3.25; 
                    break;
                case (subtot > 4.75 && subtot <= 9.5):
                    ship.value = 6.5; 
                    break;
                case (subtot > 9.5 && subtot <= 14.25):
                    ship.value = 8.75; 
                    break;
                case (subtot > 14.25 && subtot <= 19):
                    ship.value = 11.99; 
                    break;
                case (subtot > 19.00 && subtot <= 23.75):
                    ship.value = 12.79; 
                    break;
                case (subtot > 23.75):
                    ship.value = 49.99;
                    break;
                default:
                    ship.value = 49.99;
            };

            return true;
        }