I think I see the problem. You are telling it to only INCREASE Y if it is OVER 10, so Y will not change until you've moved it down enough, which you can't move it down until you've... moved it down. Try 'IF BUTTON(2) AND #UP AND Y<10 THEN Y=Y+2' and so on. Flip the comparison sign for moving down too. Remember that positive coordinates go down and negative ones go up, too.
Maybe it's the AND part that's messing it up? Instead of AND, try 'IF BUTTON(3)==#UP AND Y>6 THEN code to execute...' Also, now that I look at it you haven't initialized Y have you? Nothing will tell it what Y should start out as, so when you execute the program Y will be 0, and since you told it to only change when it is between 6 and 10, it won't change. Try putting 'Y=6' right before your loop.