wp ecommerce funtion

Hi the plugin works perfectly and its great i was hoping you could help me?

I just asking for your advice , here goes

I have a minimum order on my site of £25 so i have added some code and it works perfectly but i have a product that i dont include my minimum order with

eg minimum order is £25 worth of BEER but i also sell cigs which i dont want to include in my min order at all i want it to be still £25 worth of beer regardless of how many cigs they have in the cart, now im not asking you do this for me just point me in the right direction.

Now what i was thinking was i see there is a sub total and a grand total the minimum order runs of the subtotal not the grand total, is there any way just for this one product id, when the user clicks add to cart it adds it to the grand total like the shipping does and not the subtotal then my minimum order code will still run the same and that one product the cigs would then be added to the grand total,

i hope this makes sense and you can point me in the right direction Im sure there is a function i can create im not an php expert but do know my way round things just not great at writing php from scratch but can modify it

my site http://www.drinkdoctor.co.uk

the checkout is hidden via css for opening an closing times

https://wordpress.org/plugins/wp-e-commerce/