The Effect: Someone names any card, another any number. The performer asks if it would be impressive if that card were found at that number in the deck of cards he's holding. The audience of course agrees, but the performer admits it wouldn't be impressive as he's been holding the deck the entire time and could have done something sneaky. What would be more impressive is if that card was found at that named position in a deck of cards that performer's gone absolutely no where near. Better yet, it's been in full view since before the effect began.
The closed box is tossed to an audience member who opens the box, removes the cards, and counts them one at a time face-up to find the named card at the exact named position.