drop down list widget action

You need an 'event' to trigger that advanced action. As I explain in that blog post, this interaction is static, not interactive. The associated variable will get as content the chosen item. You need a button or a click box, to check that value and based on that check (conditional action) execute that wanted action.

If you just need a dropdown list to jump to a slide, maybe this article can give you an alternative:

More is in a... hyperlink - Dropdown Menu - Captivate blog