Button animation and onRelease?

Please do not throw me off the forum with this simple question (hopefully)
I promise you I have done ny research to rectfy it but to no avail!

I have a button that plays an animation on rollover then after the animation I want the users to click and open up an external swf file.
But the animation works great until I put the code onRelease pointing to my swf and I cannot work out why? It just will not animate. I have tried onPress. It does however load the swf with onRelease and onPress. Also I need to hide button after, has it opens up in same window.
The code below:
myButton_mc.btn_txt.text = “Thenext”;
myButton_mc.hit_mc.onRollOver = function() {
myButton_mc.onRelease= function() {
myButton_mc._visible = false;



Any help please