The Packagizer isn't suitable for this.
What you want needs more logic than what is easily possible via our GUI.
You could realize it via
EventScripter Script thought.
I suppose you're re-adding the same folder URL over time and only want JD to download all newly added items?
-psp-
EDIT
For this case, a script which has been created for another purpose - the "history script" might be useful to you ...