What I want to do is populate a dropdown field with categories from the current post.
Basically it is for a website for custom rims, each rim will be a custom post type / product categories by style, brand and rim size. Some rims only have 20" or 22", so the size will be a sub cat of the parent rim size. I want to display only the rim size in a drop down, so a user fills out a online quote form on the same page as the rim and selects they= size they want 20" or 22". Make sense? Same as this: http://www.ozzytyres.com.au/wheels/initial-d-black-red-stripe/