You can add more case statements to work with the as many list boxes as you want, however if you want list boxes that are only present and dependent on an earlier selection then it gets altogether more complicated, especially when we only have a vague outline of what it is that you are trying to achieve.
Personally if that is the aim I would go instead form a userform with cascading list boxes and write only the final values to the document based on what is selected - see
Populate Userform Listbox or Combobox