this would require creating a custom function to accomplish.
the function would need to loop through the cart to create an array of the prices for items in the cart, then reorder the array from heist to the lowest, finally loop through the reordered array and find the sum of every other price in the array, store that sum in a session variable, and use that session variable to determine the cart discount amount.
the function should not be too difficult if you are comfortable with PHP and working with functions. If this is beyond your skill level though, I would suggest purchasing a premier ticket where we could work with you to accomplish this.
