Fade Function call

I have a function on root:

_root.fadeBox_mc.onEnterFrame = function (){
if (fade){
this.nextFrame();
} else {
this.prevFrame();
}
};

and on root, a button with the code

on (rollOver){
_root.fade = true;
}

on (rollOut){
_root.fade = false;
}

This causes a mc to fade in and out on rollover/rollout. But what I wanna make is a box that fades in when pressed on the button and fade out when pressed for the second time. But if I say

on (press){
_root.fade = true;
}

the mc fades in, but I cant do another on (press) to fade out. Is this too confusing? Please help.