How to make a custom eraser tool using flash?

Question

I did make a eraser tool. But once I begin to erase a layer, the background layer is visible. I want the layer just below the topmost layer to be visible.
For eg consider 2 layers.
Layer2 is above Layer1.
When I perform erase on Layer2, I see the stage background.
I want to actually see Layer1 when I erase from Layer2.
Here is the code I used:
The comment entry shows that, I have tried that possiblity.
import flash.display.BitmapData;
var linkageId:String = "myimage";
var myBitmapData:BitmapData = BitmapData.loadBitmap(linkageId);
trace(myBitmapData instanceof BitmapData);
this.createEmptyMovieClip("mc",this.getNextHighestDepth());
mc.attachBitmap(myBitmapData,this.getNextHighestDepth());
this.blendMode = "layer";
//mc.blendMode = "layer";
this.createEmptyMovieClip("mc1",this.getNextHighestDepth());
var myBitmapData1:BitmapData = new BitmapData(800,600, false, 0xFF000);
mc1.attachBitmap(myBitmapData1,this.getNextHighestDepth());
mc1.onMouseMove = function() {
var circle_mc:MovieClip = this.createEmptyMovieClip("circle_mc", this.getNextHighestDepth());
circle_mc._x = _xmouse-40;
circle_mc._y = _ymouse-40;
drawCircle(circle_mc,40,0x000000,50);
//mc.blendMode = "layer";
circle_mc.blendMode = "erase";
function drawCircle(target_mc:MovieClip, radius:Number, fillColor:Number, fillAlpha:Number):Void {
var x:Number = radius;
var y:Number = radius;
with (target_mc) {
beginFill(fillColor,fillAlpha);
moveTo(x+radius,y);
curveTo(radius+x,Math.tan(Math.PI/8)*radius+y,Math.sin(Math.PI/4)*radius+x,Math.sin(Math.P I/4)*radius+y);
curveTo(Math.tan(Math.PI/8)*radius+x,radius+y,x,radius+y);
curveTo(-Math.tan(Math.PI/8)*radius+x,radius+y,-Math.sin(Math.PI/4)*radius+x,Math.sin(Math .PI/4)*radius+y);
curveTo(-radius+x,Math.tan(Math.PI/8)*radius+y,-radius+x,y);
curveTo(-radius+x,-Math.tan(Math.PI/8)*radius+y,-Math.sin(Math.PI/4)*radius+x,-Math.sin(Ma th.PI/4)*radius+y);
curveTo(-Math.tan(Math.PI/8)*radius+x,-radius+y,x,-radius+y);
curveTo(Math.tan(Math.PI/8)*radius+x,-radius+y,Math.sin(Math.PI/4)*radius+x,-Math.sin(Math .PI/4)*radius+y);
curveTo(radius+x,-Math.tan(Math.PI/8)*radius+y,radius+x,y);
endFill();

Answer 1

use:
import flash.display.BitmapData;
var linkageId:String = "myimage";
var myBitmapData:BitmapData = BitmapData.loadBitmap(linkageId);
trace(myBitmapData instanceof BitmapData);
this.createEmptyMovieClip("mc",this.getNextHighestDepth());
mc.attachBitmap(myBitmapData,this.getNextHighestDepth());
this.createEmptyMovieClip("mc1",this.getNextHighestDepth());
var myBitmapData1:BitmapData = new BitmapData(800,600, false, 0xFF000);
mc1.attachBitmap(myBitmapData1,this.getNextHighestDepth());
mc1.blendMode="layer"
mc1.onMouseMove = function() {
var circle_mc:MovieClip = this.createEmptyMovieClip("circle_mc", this.getNextHighestDepth());
circle_mc._x = _xmouse-40;
circle_mc._y = _ymouse-40;
drawCircle(circle_mc,40,0x000000,50);
//mc.blendMode = "layer";
circle_mc.blendMode = "erase";
function drawCircle(target_mc:MovieClip, radius:Number, fillColor:Number, fillAlpha:Number):Void {
var x:Number = radius;
var y:Number = radius;
with (target_mc) {
beginFill(fillColor,fillAlpha);
moveTo(x+radius,y);
curveTo(radius+x,Math.tan(Math.PI/8)*radius+y,Math.sin(Math.PI/4)*radi us+x,Math.sin(Math.PI/4)*radius+y);
curveTo(Math.tan(Math.PI/8)*radius+x,radius+y,x,radius+y);
curveTo(-Math.tan(Math.PI/8)*radius+x,radius+y,-Math.sin(Math.PI/4)*ra dius+x,Math.sin(Math.PI/4)*radius+y);
curveTo(-radius+x,Math.tan(Math.PI/8)*radius+y,-radius+x,y);
curveTo(-radius+x,-Math.tan(Math.PI/8)*radius+y,-Math.sin(Math.PI/4)*r adius+x,-Math.sin(Math.PI/4)*radius+y);
curveTo(-Math.tan(Math.PI/8)*radius+x,-radius+y,x,-radius+y);
curveTo(Math.tan(Math.PI/8)*radius+x,-radius+y,Math.sin(Math.PI/4)*rad ius+x,-Math.sin(Math.PI/4)*radius+y);
curveTo(radius+x,-Math.tan(Math.PI/8)*radius+y,radius+x,y);
endFill();