Dollar limit on a percentage coupon?

-- HikaShop version -- : 2.6.0
-- Joomla version -- : 3.4.6
-- PHP version -- : 5.5.29

We are in need of creating a coupon that gives 100% off to products in our 'Uniform Program' category up to $150 for members of the 'Employee' ACL group. The coupon is good for one year and can be used once per Employee. I can create a coupon that comes close to this, but am running into some issues.

If set as a 100% discount:
The closest thing I can get to what we need is creating a 100% coupon restricted to the 'Uniform Program' category and select "Coupon percentage applies to product only". At first glance this works perfectly and the discount only applies to the products in the 'Uniform Program' category - even if products from other categories are present in the shopping cart. However, if they order 1000 $20 items from the 'Uniform Program' category they are all free. We need to be able to put a cap on this of $150.

If set as a fixed amount of $150:
If I create the coupon at a fixed $150 all that is needed is one product in the 'Uniform Program' category for the order to be eligible for the coupon. This $150 is applied to the total order so if the total of 'Uniform Program' items is less than $150 and products from other categories are present in the shopping cart the discount is applied to them. We need the discount to only apply to items in the 'Uniform Program' category.

In short, is there a way to accomplish what I am looking for? A 100% discount that only applies to a specific category up to $150?

Pls advise. Thank you.

Update: We ended up licensing AWOCoupon and it has been working perfectly. Thank you for the suggestion!