Customer specific discount extension from ZealousWeb helps to create shopping cart price rules based on specific customers. Admin can create discount codes for the specific customer. This extension will load your registered customers on shopping cart rules based on the selected user group and allow you to choose customers. You will have the two options for the selected customers. You can either include those customers to the rule or exclude those customers from the rules. If you will not choose any option here, then all the customers of the selected group will use the code.
In this way, this extension can allow admin to provide a special discount to special customers and exclude the customer for the particular rules. It is an easy way to revoke discounts.