WORKS!!!!!! thanx a lot man!!!!! I wonder what should I do to make the hook active towards to elbow thing? I mean, this way the whole object is static towards the hook, and there is only one movement, the sliding on the pipe... what should I do to make all three objects independent and colliding to one another? thanx for this a lot!!!

No problem. We are all detectives here. SP is not the "easiest" plugin to use but I'm sure you can do whatever you want with it once you get the hang of it. AFAIK it can already do magnetism.