Making certain objects invisible outside of other objects?

I was wondering if this is possible at all. I tried making a ause menu using a Layout object, and the Layout object itself is set to use transparency for the layout it links to.

This creatures a pause sign / menu with nicely rounded edges. And because it's on another layout, I wanted a scrolling background. So I made some bullet objects so that they were always moving at a 45 degree angle. Now I have a nice scrolling background.

The problem I have is that it looks awkward when pausing during normal gameplay. It's better to show than to tell...

http://i77.photobucket.com/albums/j42/D ... Screen.jpg

See up in the upper-left corner? One of the little moon objects that I've made a bullet object, scrolling along, looping back to the other side of the screen, is clearly giving away the little trick here and ruining the presentation. Is there anyway to make it invisible when its outside of the background somehow?

Cover your corners with little corner-shaped sprites and give them Erase effect.

Hey! That worked! Awesome! ^_^ Thankee. Now to fine-tune the background and eventually get started on more daunting tasks. Thanks. ^^