Calling a button from another location

programming flash
1

I have a nav bar with buttons that change pages and such, but I also want another button that goes to the same pages.
The button loads a random image and then I want it to call the appropriate button it is in the nav bar.

var rand = random(4);

if (rand == 0) {
loadMovie("bioBtn.jpg", this.holder);
_parent._parent.nav_mc.whereTo = "bio";
}
if (rand == 1) {
loadMovie("eventsBtn.png", this.holder);    
_parent._parent.nav_mc.whereTo = "events";
}

if (rand == 2) {
loadMovie("forumBtn.png", this.holder);    
_parent._parent.nav_mc.whereTo = "forum";
}

if (rand == 3) {
loadMovie("mediaBtn.jpg", this.holder);
_parent._parent.nav_mc.whereTo = "media";
}

btn.onPress = function(){
    _parent._parent.nav_mc.whereTo.go();
    }

How do I call the button functions from this location? I get undefined whenever I try to call something from those nav bars? ahhhhhhh!