ActionScript 3.0 :: How To Build Horizontal Nav Menu Bar

I am following an online tutorial to build a horizontal menu bar in AS3. In the tut, they are using MovieClips, but for what I want to achieve I am using buttons.

Here is their code.
Select allfunction navOverF(event:MouseEvent):void{
event.target.filters = [navBtnGlow];
navBar_mc.setChildIndex(event.target as MovieClip, 1);
dropMenus_mc.gotoAndStop(navBar_mc.getChildAt(1).name);
trace("We are rolling over..." + navBar_mc.getChildAt(1).name);
}
I have worked out that the issue is in line three "(event.target as MovieClip, 1)", but how do I change this code to work with buttons?