onMouseDown (object3D to Vector3D)...help please

Hi once again.
I have an object that ‘floats’ around a scene and when do mouseClick on it I need the Vector3D(x,y.z) instead of Object3D. _mouseVector is Vector3D var
Can anyone help with this please?
Regards
FJW
<code>
private function onMouse3DDown(ev:MouseEvent3D):void
{
var obj:object3D = ev.object; //this is ok
_mouseVector = new Vector3D(ev.scenePosition.x, ev.scenePosition.y, ev.scenePosition.z); //this fails with access of invalid property scenePosition
trace(_mouseVector);
}