Custom iPhone Case Help (Cutouts)

Hello everybody,

I own a solidoodle 4 and I have been getting really good iPhone prints. I want to customize a case I downloaded off thingiverse in sketchup by putting a cut out of a logo on the back of the phone. I thought I was successful one time until I sliced it and the gcode image showed it being created without the cut out.

Does anyone know how to do this in sketchup or know of a good tutorial I could follow?

Thanks