[away3d] Disable Interavtivity on certain Objects?

[am]

Hi,

i got a plane and another one on top of it.

now i already use

plane.pushfront = true;

and i want to listen to a MouseDown on that plane

plane.addOnMouseDown(onMouseDown);

But it seems that the mouseDown is often catched by the second Plane
in the back.
Is there a way to disable interactivity on that second plane?

thanks!