how to : automatic change "add to cart" picture when mosue move on?

[fiji]

Hi, guys

I saw a very good effect on other site.
When move the mouse to the "add to cart" picture, the picture will change to another picture auto.

How to do it in the zen-cart?
anyone knows?

Thanks



This is the zen-car code, how to change it?

                <?php
if (CUSTOMERS_APPROVAL == 3 and TEXT_LOGIN_FOR_PRICE_BUTTON_REPLACE_SHOWROOM == '') {
  // do nothing
} else {
?>
                <?php
    $display_qty = (($flag_show_product_info_in_cart_qty == 1 and $_SESSION['cart']->in_cart($_GET['products_id'])) ? '<p>' . PRODUCTS_ORDER_QTY_TEXT_IN_CART . $_SESSION['cart']->get_quantity($_GET['products_id']) . '</p>' : '');
            if ($products_qty_box_status == 0 or $products_quantity_order_max== 1) {
              // hide the quantity box and default to 1
              $the_button = '<input type="hidden" name="cart_quantity" value="1" />' . zen_draw_hidden_field('products_id', (int)$_GET['products_id']) . zen_image_submit(BUTTON_IMAGE_IN_CART, BUTTON_IN_CART_ALT);
            } else {
              // show the quantity box
    $the_button = PRODUCTS_ORDER_QTY_TEXT . '<input type="text" name="cart_quantity" value="' . (zen_get_buy_now_qty($_GET['products_id'])) . '" maxlength="10" size="4" /><br />' . zen_get_products_quantity_min_units_display((int)$_GET['products_id']) . '<br />' . zen_draw_hidden_field('products_id', (int)$_GET['products_id']) . zen_image_submit(BUTTON_IMAGE_IN_CART, BUTTON_IN_CART_ALT);
            }
    $display_button = zen_get_buy_now_button($_GET['products_id'], $the_button);
  ?>
                <?php if ($display_qty != '' or $display_button != '') { ?>
              </p>
              <div id="freeShippingIcon"></div>
              <div id="cartAdd"> 
                <?php
      echo $display_qty;
      echo $display_button;
            ?>