Managing Hierarchy with members moving between levels


What are the ways of Hierarchy Managemnet when, list member are moving between levels? For e.g. the file we recieve from Third Party system, is used to create the hierarchy. This Data Module contains line items referring to various Levels L1, L2….. First Iteration of Data Import gives us say an L7 item with its respective parent/children mappings and second iteration of the load gives us the same L7 Item code under L8 Column. That is, we see a new level is inserted as L7 item now. How do we manage such situations?