Adding price percentage based on other options

We are using product options to allow customers to select size and material type (among others).

I see there's an option to add a percentage to main product price, but this isn't suitable or desirable in our instance.
Some materials are more costly, so we'd like to add a percentage based on the size (another variant / characteristic) applied to the product.

Is this possible, or is there another way to accomplish without custom code to determine price?