How to clean a list variable?

I have a list variable for a page.  Initially this list is empty, but after the preparation, the list will contain entities (by ListApped).  But when I send an ajax sumbit and re-execute the preparation, the list still contains the old entities. How to clean/empty the list?

You can use the Sistem action List_Clear to clean the variable. Go to Add adn Remove References to reference that action if you don't have it already. Put the List_Clear Before the ajax call.

Thanks, Jose.