Calling object names and variables dynamicly?

Im kind of new to flash, and Im having trouble figuring out how to do this.

Say I have some sort of user-input that will give me a number, for example the number 3.
Then I want to call one of many movieClips i’ve previously created, according to that input.
So I would like to dynamicly call ex. myMovieClip3._visible = true.

What I cant figure out is how to construct a way to call myMovieClip(x) and its variables.

Thanks for reading!