AbleCommerce Shopping Cart Software

Is there a way to restrict coupon usage by a region/zone? I'm looking to add a coupon to eliminate sales tax for eligible shoppers but not everyone else (ie. no 8% discount for everyone). I know that I could just set sales tax to 0% but I want to only credit people who use the coupon.

Anyone?

I guess this would be possible with some small custom code. First create a new user group. Then create your coupon and mark it only available to newly created user group in previous step. Then upon checkout when customer provides its address you can decide user should be added to desired group or not. Add user to group and then he/she will be able to use coupon in question while other people can't. Here is a quite similar thread have a look on it for implementation reference viewtopic.php?f=42&t=13794

Thank you for the advice.