how to change the code zero for an item and click CheckOut,throw an alert message?

[[email protected]]

How to change the code zero for an item and click CheckOut,throw an alert message????

 

<p id="cart-buttons">

{if $order_process == 'order'}

<a href="{$link->getPageLink("$order_process.php", true)}" class="button_small" title="{l s='Cart' mod='blockcart'}">{l s='Cart' mod='blockcart'}</a>{/if}

<a href="{$base_url}http.php" id="button_order_cart" class="exclusive{if $order_process == 'order-opc'}_large{/if}" title="{l s='Check out' mod='blockcart'}">{l s='Check out' mod='blockcart'}</a>

</p>