the name ENTERFRAME is a little misleading. It's not referring to the timeline, but the frame-rate of the flash movie.

So if your movies frame rate is 30 fps, then the ENTERFRAME listener will try to fire 30 times per second, even if you tell the timeline to stop(); which would cause lag.

If you have an empty dynamic textfield on the stage, and a string of text in your timeline actions, you shouldn't have a problem just adding myTextField.text = myString.