Comet Storm + Manabond

Hey everyone,
I decided to try to run a deck of of MTGfanatic called "Land to the Max" ( http://www.mtgfanatic.com/decks/viewdec ... agesize=25 ) and the creator mentioned being able to cast Comet Storm after activating the land effect of Manabond, but before discarding the card from hand due to it being an instant.
I can't seem to figure out a way to make this happen in Forge - is it because the creator has the wrong idea and you in fact CAN'T cast the instant at this time?
I decided to try to run a deck of of MTGfanatic called "Land to the Max" ( http://www.mtgfanatic.com/decks/viewdec ... agesize=25 ) and the creator mentioned being able to cast Comet Storm after activating the land effect of Manabond, but before discarding the card from hand due to it being an instant.
I can't seem to figure out a way to make this happen in Forge - is it because the creator has the wrong idea and you in fact CAN'T cast the instant at this time?