Custom calculation Script help!

I am having issues with this script. The custom calucation scirpt that I put in is correct and when I go to preview and drop down my first box and click on a product the second box next to it changes to the formula I am needing. BUT when I go to the drop down on the second box and click on the correct option it goes back to the first product typed in the options of that product. It won't let me choose another one in the drop down menu.. I am hoping someone can help me with this. Sorry if this kind of confusing I am trying to word this in the best way possible. I have also attached a screen shot of the first dropdown and second dropdown.