How to have an on screen trace indicator (of position) for off screen actor

cosmopolice

Hi,
I'm trying to find a way to have an arrow indicator appear on screen whenever an actor moves off screen (off camera).

So far my best idea was to make an invisible actor be as large as the screen and whenever the actor isn't overlapping then a global attribute is set to actor off screen (true).

Now as far as the indicator goes i was using constrain attributes to x, y of that actor and trying to have it collide with a frame of invisible walls to keep it on screen and visible only when the actor goes through these invisible walls.

The issue I have is that my camera needs to move so the area covered by that invisible actor that makes up the whole screen needs to collide with the invisible walls to keep that frame around it. However, i can't think of a simple way to have the 4 sides of the frame follow suit... unless using some complex synchronized movements that could easily stop working fast I'm guessing...

any better way to go about doing this? Would a hollow rectangle png do the trick for the frame?

thanks

cosmo