In the Flash IDE, I'm able to make a vertical textField by clicking a little button that says "change orientation of text" and setting it to vertical. That only works for static text though. If you change it to dynamic or input, the button becomes greyed out. Is there a way to do it in Actionscript dynamically? Also, I should add that if you make a vertical textField in the IDE, it traces as a MovieClip.
It can't be done with the TextField class.
It can be done with the newer flash.text.engine using TextBlock/lineOrientation. Unfortunately this is a very low level API not like TextField, and there is no Flash/Animate IDE integration at this point, so you must do it all through AS3.