Nope, because the possessed turn is played not by you - you are only instructing the possessed player what to do, but it is him who plays the cards and every "you" on card instructions refers to him (the possessed player), not you (the possessor).
Close, but the effect is a "when you gain" condition. The possessed player bought the card, but then by possession's rules, the possessor is the one who actually gains it. So the "you" is the player who gained the card, not the player who bought the card. As a result, the player to the left of the "you" is the possessed player.