Put a Taboo to Use

End of 3rd year, during the fight in Shrieking Shack, Pettigrew drops a magical sack that Harry hides, not looking inside until returned to No.4 Privet Dr. There's a journal begun by Lucius Malfoy with a spell to cast taboo on Lord Voldie's name, and Pettigrew's plans to cast spell on 'Lord Voldemort' and 'He-Who-Must-Not-Be-Named.' What can Harry do with this spell?