How do I think my movie clip?

I have these buttons on my website that are actually movie clips because I have them fade in and out on the rollover, how do I get them to link to the next scene? I tried the on release gotoandplay command, but it says I cant use that on a movie clip. Here is my actionscript on the layer of each button/movieclip:

testbutton_btn4._alpha = 50;
testbutton_btn4.onRollOver = function() {
fade(this, this._alpha, 100, 0.85);
testbutton_btn4.onRollOut = function() {
fade(this, this._alpha, 50, 0.08);
function fade(mc, startv, finalv, rate) {
// calculate per frame change
var d = (finalv-startv)*rate;
mc.onEnterFrame = function() {
// get the absolute value of the differences so negatives dont affect the calc
if (Math.abs(finalv-mc._alpha)>=Math.abs(d)) {
// add the difference
mc._alpha += d;
} else {
// all done , clear the onEnterFrame
mc._alpha = finalv;
delete this.onEnterFrame;

can someone help please??? Thanks.