button : auto hide with delayedcall ?

hi, is there a way to auto hide the button bar after some times the mouse didn't move ?

this is my incomplete code :

<style name="button" url="%SWFPATH%/skin/buttons2.png" scale="1.0" keep="true" alpha="0.0" onloaded="delayedcall(0.5, tween(alpha,1.0,1.0); );" />

thanks a lot