Dynamically Stopping Child MovieClip

I’ve created an object (a person named jop) from a number of other symbols, and I’ve added the person to the stage manually (i.e. not via AS). One of the symbols, the mouth, has multiple frames, and I would like to stop it from playing at runtime. Here’s what I tried:


I know that I’m accessing the clip, because if I do this:

jop.getChildAt(jop.numChildren-2).alpha = 0

there is an affect (the mouths alpha is reduced). I get the following error with the former code:

1118: Implicit coercion of a value with static type flash.display:DisplayObject to a possibly unrelated type flash.display:MovieClip.

What I don’t understand is why flash sees the mouth as a DisplayObject and not a MovieClip, when I’ve definitely gone into its properties to make sure it was a MovieClip. It would make a nice shortcut if I were able to handle MovieClips this way, so I hope theres a way…otherwise I guess I’d have to add all the components of poor ol’ jop to the stage at runtime to have access to them as movieclips.

I hope this isn’t a dumb question… I’ve searched the forums for something like this, but nothing was on par. Thanks in advance.