Problem Creating a Tween

Hi, sorry if I’m posting this in the wrong thread, I don’t use forums regularly but I am creating an animation using an Action Script 3 file type so I figured I’d post it here… Anyhow, I am trying to create a classic tween to move my character’s arm from one place to another, and after I tween it, the parts inbetween the move get all dicombobulated and then go to the next pose I need them to go to. I have included a link to a youtube video showing exactly what is going wrong. PLEASE PLEASE HELP. I’ve seen it work PERFECTLY for some people in videos, and for some reason for me it gets all effed up. Thank you.