Hi,
Could you be more specific what is this "something"?
Was this a field ? You could find it by Max(Fileds!dateColumn.value). For only showing that row, you could use visibility expression as :
=IIF(Fileds!dateColumn.value=Max(Fileds!dateColumn.value), false, true)
If it is an report item, we could not know if it is last added into the report design.
You could add more details or screenshot so we could understand you design or issue better.
Regards,
Joy