Drag & Drop Question

I have a simple Drag and Drop on a page with a Submit button. When user clicks Submit, a page variable is modified from 0 to 1 AND the next page button (up to that point invisible) appears. Unfortunately, user can click Submit and move ahead whether Drag/Drop question has been answered or not!Is there any way to tie the modified variable to completing the Drag and Drop?

Discussions have been disabled for this post