Zen Cart Version 1.5.0

I have a configuration question about setting up specials. I have my shipping set to charge shipping costs based on how many items are purchased. What I would like is to offer free shipping for orders over a base price. I do not want to the customer to have to type in a coupon code. Is this possible? I would be willing to do some scripting to figure it out.

Thanks,

IsImOnline.