How can I enable next dropdown selection if current is selected and disable again when previous gets unselected?

I would like to be able to have four dropdown menus that behave as follows: If the current dropdown gets selected, the dropdown next will be enabled. If the current dropdown gets unselected every consecutive dropdown gets disabled Right now I’m able to enable the next dropdown upon selecting the current dropdown, as well as… Read More How can I enable next dropdown selection if current is selected and disable again when previous gets unselected?