Quick question about _alpha

hey guys, its been a while since ive been on. i want to tell flash to make an mc’s alpha = 0 unless any button has been released. im trying someting like:

if (button has not been released) {
_root.container.ref._alpha = 0;
}
}else{

_root.container.ref._alpha = 100;
}

im just not sure about the syntax. any help?