Getting "focus" on a rollover area - how to put onRollOver code under a button?

Hi all, I have a background Nav area, that on rolling over, I want to come more clearly into focus. This is done by lightening & changing the colour on rolling over, where the background nav area is actually 2 identical boxes, and only the top one shows and lightens and de-blurs on rolling over.

The problem is, I have buttons (of course!) over this whole thing, and when someone hovers over the button…it makes the original code of the nav background think it no longer is rolled over, and goes to the onRollOut() function. It also seems to be killing my performance, so I might be doing something totally wrong.

What I would like is essentially a focus control - you are over the nav background and it lights up the way I want, but the buttons over it (both the nav and the buttons are on the main timeline - the buttons in a layer above the nav) still work normally and it stays lighted up…here is my code if I am doing something obvious, though I have only made a couple of posts so I will not blame anyone for not having a go at it…Shawn

this is in the nav background movieclip, which has a navUnder mc and a navOver mc included in it:

this.navOver._visible=false;
var my_color:Color = new Color(this.navUnder);
my_color.setRGB(0x333333);
this.navUnder._alpha=85;

var underBlur = new flash.filters.BlurFilter(15,15,3);
var myTempFilters:Array = navUnder.filters;
myTempFilters.push(underBlur);
navUnder.filters = myTempFilters;

this.onRollOver=function(){
this.useHandCursor = false;
var overBlur = new flash.filters.BlurFilter(6,6,3);
var myTempFilters:Array = navOver.filters;
myTempFilters.push(overBlur);
navOver.filters = myTempFilters;

this.navOver._alpha=40;
this.navOver._visible=true;
var my_color:Color = new Color(this.navOver);
my_color.setRGB(_root.mainColor);

};

this.onRollOut=function(){
this.navOver._visible=false;
};

p.s. it’s available here, well at least in Josh’s image gallery: http://shawngibson.com/SITES/apps/mySite/