Free shipping and promo rule

We have a free shipping promo on international orders $100 and over. We also have free shipping on all domestic orders. My question being, on international orders how can I set up the rule so that if the total is under $100 after the discount, they don't get free shipping? Ex: We run a Holiday Promo for 20% off store wide, item is regularly $100, with the promo the new total is $80. Since that new total is under $100, I would like the free shipping rule to be unavailable to this customer.