I unterstood that I should program in the "do-something-if" way and not in the "do-nothing-unless" way. But the point is, that I just don't know how to handle that.
So, I dont wan't to question your skills with the arduino programming language (in fact, almost C#) but your post is usless for me unless you explain how to do it (or just send me a link that describes it) - not what I have to do (except, you know a better way to do it as you did in your first post).
Thanks for your advice!