[MaxFX]

Класс такой

package GUI
{
	import flash.display.*;
	import flash.text.*;
 
	public class SoundButton extends SimpleButton
	{
		public function SoundButton ()
		{			
			((upState as DisplayObjectContainer).getChildAt(3) as TextField).embedFonts = true;
			((downState as DisplayObjectContainer).getChildAt(3) as TextField).embedFonts = true;
			((overState as DisplayObjectContainer).getChildAt(3) as TextField).embedFonts = true;
		}
	}
}

В коде я делаю так:

...
btnSound.addEventListener(MouseEvent.MOUSE_DOWN, btnSound_MouseDown);
...
 
private function btnSound_MouseDown(e: Event): void {
	SoundEnable = !SoundEnable;
 
	var txt: String = null;
 
	if (SoundEnable) {
		txt = "ВКЛ. ЗВУК";				
	} else {
		txt = "ВЫКЛ. ЗВУК";
	}
 
	((btnSound.upState as DisplayObjectContainer).getChildAt(3) as TextField).text = txt;
	((btnSound.downState as DisplayObjectContainer).getChildAt(3) as TextField).text = txt;
	((btnSound.overState as DisplayObjectContainer).getChildAt(3) as TextField).text = txt;
}

Шрифт внедрил непосредственно при редактировании TextField'а в самом fla (непрограммный способ)