Discounts for a combination of products

Site URL: http://www.whitecloudkiteboarding.com/shop

Hi all

I am hoping that you might be help to please help me with some problem solving. I have been trying to find a solution for the functionality that I am after for a quite a while now.

I run a shop that sells kites. The customer needs a number of different products and I wish to offer a discount based on a combination of products.

I looked at the Advanced plan and saw it offered the Automatic Discount feature. I could figure out from the video whether it would suit my needs but but I decided to upgrade anyway.

All I've managed to do is get my site to automatically apply a discount if the cart is over certain dollar amounts. I see you can apply for a certain category but that's not what I'm after. I'm looking for a solution that says, if you add product A + B, get 5% off, if you add product A + B + C, get 10% off.

Someone suggested that a 3rd party app might be able to achieve this, but I have no idea where to start.

Please can someone suggest how I might achieve this.

Thanks is advance!

Did you have any luck finding a solution to this. I have a similar problem. 

I want to offer ai discount for purchase over a certain $ amount, but only for products in specific category.

I figured out how to offer a percent discount over a dollar amount and a percent discount  based on category, but not how to have a percent discount over a $ amount for products in a certain category.