close but not quite right...don't have b3d in front of me right now but it should go something like this:
something like that should work
graphics3d 800,600,0,2 camera=createcamera() cube=createcube() entitypickmode cube,2 ;sets per polygon picking moveentity camera,0,0,-10 ;move the camera back so it can see the cube repeat mx=mousex() my=mousey() updateworld renderworld if camerapick(camera,mx,my)<>0 then color 255,255,255 text 0,0,"You put the mouse cursor over the cube" else color 255,255,255 text 0,0,"Mouse cursor not over anything" endif flip until keydown(1) end
something like that should work