My question is as follows:

I want to create a complex order form that has 10-15 products. Each product has the option to choose the size (A) and quantity(B). Depending on the person's choice a value is calculated presented (C). I then need all the products final values (C) to add up and display in box at the bottom of the page (D)

I've managed to find great solutions for the A+B=C, but I just can get one that then adds up all the C values.

Is there a simple Javascript solution for this problem?