Double it and give it to the next person

You attempt to interrupt a creature in the process of casting a spell. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect. If it is casting a spell of 4th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the creature's spell fails and has no effect. Furthermore on the creatures next turn if it choose to cast the same spell it must upcast it and target a different creature, if there is no valid creature in range they must target themselves. If the creature cannot afford to upcast the spell they cannot cast the spell until they complete a long rest