I have bought an Magento extension which calculates an extra fee in percentages, based on the baseprice.
The extension supports RAL-colors so that a product can be bought with a RAL-color.
So if I have a product that cost € 300, and I choose a RAL-color that has 15% extra charge, then the price will be € 345.
That's just fine.
I also have options on the products for different sizes. If another size is selected, an different price will be shown. That price is taken from the "Simple Products"! This is also done by an extension.
Now, the thing I want is that the RAL-color extension does not calculate the price on the base price of the product, but on the shown price from the Simple Products. So if a different size has the price of € 400, then the new price should be 400 * 1,15 = 460. At this moment the price is (15% of 300) + 400 = 445.
So that's all I want and I hope it's all clear. Otherwise, please ask me.