Sending actionscript rectangle to back layer

Hi - Would really appreciate some help!

I’ve created a rectangular box with actionscript (code follows) and I need to make sure this stays in the background - so all other movieclips and symbols are visible when they are positioned over the top of it… I guess it’s using the swapDepths function although not sure? Can anyone help? Thanks.

this.createEmptyMovieClip(“rectangle_mc”, 10);
rectangle_mc._x = 15;
rectangle_mc._y = 285;
drawRoundedRectangle(rectangle_mc, 520, 100, 15, 0x2C79BE, 100);
function drawRoundedRectangle(target_mc:MovieClip, boxWidth:Number, boxHeight:Number, cornerRadius:Number, fillColor:Number, fillAlpha:Number):Void {
with (target_mc) {
beginFill(fillColor, fillAlpha);
moveTo(cornerRadius, 0);
lineTo(boxWidth - cornerRadius, 0);
curveTo(boxWidth, 0, boxWidth, cornerRadius);
lineTo(boxWidth, cornerRadius);
lineTo(boxWidth, boxHeight - cornerRadius);
curveTo(boxWidth, boxHeight, boxWidth - cornerRadius, boxHeight);
lineTo(boxWidth - cornerRadius, boxHeight);
lineTo(cornerRadius, boxHeight);
curveTo(0, boxHeight, 0, boxHeight - cornerRadius);
lineTo(0, boxHeight - cornerRadius);
lineTo(0, cornerRadius);
curveTo(0, 0, cornerRadius, 0);
lineTo(cornerRadius, 0);
endFill();
}
}