Fading buttons

Is there a way of making the roll over on a button fade in and out again smoothly using the _alpha or any other command? I can get the button to fade in by animating the over state, but when you move the mouse off the button the fade jumps back to normal very quickly.


I want smoooooooothness if poss

Can anyone help?

I've included an fla below that uses the _alpha scripting to control the fade. You can control the speed and use movie clips to act as buttons.