Forum:Exchange question

If I activate Exchange, and the only card that I have in my hand is a mystic tomato (or some other monster that its effect activates in the graveyard) and my opponent pick that card, and then in his turn set that monster. If I attack my mystic tomato, and its send to the owner graveyard (mine) Can I activate the effect ore my opponent? If the answer is that I have the effect, then, in this case, Exchange works like creature swap?