Having a little trouble with coupons

Hello All!
I cant seem to get my head around what seems to be such a simple request from my customer.
they have asked for a coupon that can be applied at the checkout and will automatically add a free product to the basket. with the rule that the customer must be at least one product for the coupon to work.

Ive been through the woo commerce coupon settings, we have another neat plugin that does pricing deals really nicely called "varktech - pricing deals".
it has many of the features i need, but will only allow for the use of a coupon OR automatically add free product.

Can anyone suggest a solution?
Luke Hands