I've done a thorough search on this subject to come to the conclusion that zencart does not support this attribute feature and that the only way to accomplish this is to add custom code.

So.. my question is if someone can help me code it. I am trying to do it as simple as possible. Just two options in the first dropdown box, each choice changing the text contents of the second dropdown box. An example of this in action is in cars.com.

Also, which file would add this code for? I would like these dropdown boxes appear in my individual products page.