wp ecommerce minimum order

hi hopefully someone can point me in the right direction,

i have a minimum order on my site which £25 but i sell an item which i dont want to be part of the £25 so basicly i want to remove / skip the item whilst calculating the total of the cart so that item is not part of the total min order

more detail

i sell alcohol on my site min order is £25 but i sell cigs aswell if the customer adds cigs to checkout i want the customer to still buy £25 worth of alcohol before the checkout opens

<div class='gocheckout'>

<?php $total = ($GLOBALS['wpsc_cart']->calculate_subtotal() );
if($total < 80):
echo "<span class=\"total_nudge\">Checkout minimum is 80.00</span>"; endif;?>

<?php $total = ($GLOBALS['wpsc_cart']->calculate_subtotal() );
if($total >= 80): ?>

<a href='<?php echo get_option('shopping_cart_url'); ?>'><?php echo __('Go to Checkout', 'wpsc'); ?></a>
<?php endif;?>

    </div>

<?php else: ?>

    <p class="empty">
<?php echo __('Your cart contains', 'wpsc'); ?>   <span class="emptyisthecart"> <?php echo __('0', 'wpsc'); ?> </span>  <?php echo __('items', 'wpsc'); ?>

    </p>

<?php endif; ?>

https://ww.wp.xz.cn/plugins/wp-e-commerce/