How much data do you have? Another approach would be to use Peek/Previous to create a unique ID
LOAD [Original ID],
If([Original ID] = Previous([Original ID]), Peek('UniqueID'), RangeSum(Peek('UniqueID'), 1)) as UniqueID
Order By [Original ID];
DROP Table Table;
If the above does not work... how about using RowNo() when loading the data to give the row a Unique ID...
if needed, you can import the distinct version of your ID with the row number and then use table joins to move the Row Number ID around to other tables in QlikView
and then drop the field\tables once finished.
This probably means the Row ID to your UNID changes with every data load