Well, it's a common theme right now, but using a doit method you probably could get away a statement like that. Granted the one you typed isn't in the right order but the jist is right. And a display might be better, a print statement will go away if I hit enter, but the display will stick around.
(if (== score 69) // I'm not sure what the score variable is called exactly
(Display "You've done it you are the winner.")
)
Or instead of a print or display, you could just go to an entirely different room. One that says congratulations or you won or whatever. Maybe try your hand at using a changestate method and making some sort of animations.