Add User to Group "Shopper" After ANY purchase?

-- HikaShop version -- : 2.3.2
-- Joomla version -- : 3.3.3
-- PHP version -- : 5.4.32

Goal: To offer a $20 coupon to any customer on their second purchase (with minimum purchase amount of $100)
Coupon is set up with the correct rules, limiting to user group "Shopper" and a user quota of 1.

I'd like to add anyone who purchases any product to the user group "Shopper" in order to offer that coupon to them for their next order. Instead of marking each of my thousands of products to "Add User to Group after purchase" is there a way to add ALL users to that group after their first purchase of ANY product?

Thanks. Absolutely love this component.

Thanks, Jerome!

For anyone trying to do this that might find this forum (and so that Jerome can double check my work), I'm going to list out the exact step-by-step instructions below.

HikaShop --> System --> Mass actions
Create a New Action

Name: Add to Shopper Group
Description: When an order is confirmed, add user to Shopper Group
Published: Yes
Data: Order
Triggers: After an order is updated
Filters: Start 0 Value: 500 (I'm not sure what these fields are for)
AND: Order Status = Confirmed
AND: Users with ACL; Not in; Shopper
Actions: Change the User group; Add; Shopper

Does that look correct?

Thanks again for the awesome support. I've used HikaShop for a while and I absolutely love it.