Thank you korbaach and Magistross
Magistross: I understood (0 is always false / 1 is true, right?). It works very well. Thanks.
As I said, the sprites will fall and when it changes to a different position from the one I've specified in the "pick comparison", I need the sprite to return to its default frame (0). I tried to use "else" to do this but it's no work. Do you have any idea how to solve this?
***Edit: Everything is okay now. Thanks.