Question on friday night

Within my main movie I have a movie clip that holds three 3 buttons that are made with movie clips.

The movie clip that holds these 3 is called buttons_mc

The 3 button movie clips are b1_mc, b2_mc and b3_mc within that mc.

Within the buttons_mc are two layers one for the buttons and one for the action script that has the following code:

b1.onRollOver = over;
b1.onRollOut = out;
function over() {
this.gotoAndPlay(2);
}
function out() {
this.gotoAndPlay(5);
}
b2.onRollOver = over;
b2.onRollOut = out;
function over() {
this.gotoAndPlay(2);
}
function out() {
this.gotoAndPlay(5);
}
b3.onRollOver = over;
b3.onRollOut = out;
function over() {
this.gotoAndPlay(2);
}
function out() {
this.gotoAndPlay(5);
}

However they are not functioning at all. Any ideas? Does the Action script need to be in the main time line and if so do i need to call reference to the buttons_mc since they are within? and how do I code that? I have tried multiple variations but cant seem to get it. Thanks in advance.
MT