Buttons and If Statements

I’ve created a button that’s actually a movie clip. If I know my button’s going to incorporate complex rollout/rollover animations, then I normally convert it to a movie clip symbol. I need this button to load an external swf file onRelease. How do I integrate the following if statement:

on (release) {

if (_root.currMovie == undefined) {

_root.currMovie = “about_us”;
container.loadMovie(“about_us.swf”);
} else if (_root.currMovie != “about_us”) {
if (container._currentframe >= container.midframe) {

_root.currMovie = “about_us”;
container.play();

}

}

}

into this button function

this.onRelease = function(){

}