Using excel to optimize panel stock

I was wandering if someone could help me with this.
I have a worksheet that the panel sizes needed to construct 5 piece cabinet doors are entered.
What I am trying to accomplish is to have the same length panels optimized on panels that can not exceed 42 inches in width.
For example If I had 2 panels 20 inches wide and 31 inches long and 3 panels 10 inches wide and 31 inches long.
Then the rough panel size would calculate to be 33 inches long and 41 inches wide with this panel quantity of 1.Then it would calculate the next panel to be 33 inches long and 31 inches wide with this panel quantity of 1
The worksheet that I currently have does this to some degree but I can only get it to work on a width to width bases. In other words I can not seem to figure out how to combine the total widths of the same lengths and come up with workable rough panel widths.
I would be thankful for any advice.