Display Subcategories of Category in list dynamically

[daebat]

Here is my hierarchy: Mirrors -> 1990 -> Ford -> Ranger -> PRODUCT LISTING

 

I would like to create a form that allows for the user to use a drop down to select mirrors and then below it auto completes the year list. Once you select the year it will generate the list of makes (ford) and from there it will list the model (ranger).

 

There will be four drop downs.