Your description of what you want to do is not clear to me. Can you explain more and possibly include a screenshot with notes on it?
Not absolutely clear on what you intend to do, but you can try one of these methods -
1. Go to the desired frame in your motion tween > right click > Split motion.
You can then drag and move different pieces of your motion tween with suitable number of blank frames in between.
2. create a new layer, goto the frame where you wish to stop tweening, and add the desired operation using actionscript.