Thank you very much!!!
Your methods using variables are really working. I especially liked the ansmesnobody's solution:
This is similar to my third method in the first post.
I think the David's method is the best, because it consists only of 3 events and doesn't use any variables.
It's really simple and works perfectly.
Thanks! <img src="http://i987.photobucket.com/albums/ae352/constructgame/ew.gif">