[balinor]

You'll see the add to cart and add to wishlist buttons in this area:

	<td>{include file="buttons/add_to_cart.tpl" style="button" href="javascript: if(FormValidation()) document.orderform.submit();"}</td>
	<td>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>
	<td>
{if ($login ne "" || $config.Wishlist.add2wl_unlogged_user eq 'Y') && $active_modules.Wishlist ne ""}
{include file="customer/add2wl.tpl"}
{/if}
	</td>

Just add another table cell and add your code there, like this:

	<td>{include file="buttons/add_to_cart.tpl" style="button" href="javascript: if(FormValidation()) document.orderform.submit();"}</td>
	<td>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</td>
	<td>
{if ($login ne "" || $config.Wishlist.add2wl_unlogged_user eq 'Y') && $active_modules.Wishlist ne ""}
{include file="customer/add2wl.tpl"}
{/if}
	</td>
<td>Your code here</td>