In Lego Harry Potter years 5-7 the diffindo spell will not left me throw objects at death eaters in level a veiled threat. how do i beat this level?

In order to defeat the Death Eaters in this level, you must use the Diffindo spell to cut the ropes holding up the chandeliers, causing them to fall and defeat the enemies below. Aim carefully and release the spell at the right moment to successfully execute this strategy.