cart using checkbox on attribute

[bis-zone]

I have developed a complet ecommerce site
I want to have a checkbox in only items that have a second attribute set.(gift wrapped) This will always be the second attribute.
I used
{if isset($attribute_count) && $attribute_count gt 1}
    giftwrapped    
{/if}
But  cannot seem to get the javascript to work. What I want to happen when they click the checkbox the second attribute selected index=1 and when they untick the box the selected index =0
The attributes are hidden by using a div in thecart template as below

{* add to cart template *}
{$formstart}


{if isset($attribute_count) && $attribute_count gt 0}
  {foreach from=$attributes item='attrib'}
    {$attrib->name}: {$attrib->control}
  {/foreach}
{/if}


{if isset($attribute_count) && $attribute_count gt 1}
    Gift Wrapped    
{/if}

{$formend}



I do not want to use a dropdown but a checkbox