ActionScript 2.0 :: Tween Class - Move To Screen Area And Zoom Nav

I'm trying to achieve a simplified version of the move to screen area and zoom nav similar to: [URL]. I've read and completed the macromedia tweening tutorials [URL] and gained overview of tween class etc., So, I created an example (credit :sophistikat) using the macromedia tween class:

Code:
import mx.transitions.Tween;
import mx.transitions.easing.*;
myBtn.onRelease = function () {
//first move to center in one second witih no delay
main_mc.tween("_x", 50, 1, "easeinoutElastic");
main_mc.tween("_y", 50, 1, "easeinoutElastic");
// and in 2 seconds scale closer
main_mc.tween("_xscale", 150, 1, "easeinoutElastic", 2, true);
main_mc.tween("_yscale", 150, 1, "easeinoutElastic", 2, true);
}

The script in layer 1, the bt in layer 2 and the main_mc in layer 3 - all correctly 'instanced'. But not working - the main_mc isn't moving and then zooming in when btn is clicked.