How do I allow a free product into a cart, but only if cart net value is above $10? I'm interested in running a promotion ...

I'd like to make a product free if the customer's cart total is $10.

I was able to do that with this module: http://drupal.org/project/uc_discounts_alt

Everything is working great, but I don't want my customer to be able to add the product to their cart unless they are buying $10 worth of regular products.

The products I'm giving away could be placed in another ubercart class, but I can't find a module that will allow me to prevent the node from being sold unless the cart total is $10 or more.

Any ideas or help would be greatly appreciated.

I've already explored the "free" checkout options; I'm really simply looking how to make a product not sellable unless the cart total has a minimum of $10.
Take a look at the Ubercart Restrictions module.


  This module will do its best to prevent the wrong sort of people from
  ordering the wrong sort of goods, or to ship them to the wrong kinds
  of places.
  
  For example, some products cannot be ordered by minors, or some
  products cannot be shipped to certain states