Hi. I added a javascript code in update_detailed_images.post.tpl file. This code will change second select option box based on the first select box dynamically. I am trying to pass variable from javascript to product page (admin.php?dispatch=products.update&product_id=17)
I reread your original post and my approach won't work for you. Any reason you can't use "sequential option processing" to get what you need. You can look at how they implement countries/states where depending on what country you choose, you get a different 2nd menu of states.