Just to re-iterate posts I made a couple of years ago on the forum, for the keen spotters amongst us,several independent spotting database provides have customised interfaces that sit on top of the Radarbox screen and identify which aircraft within "my flights" have not been logged on the independant database. I personally use Aerodata and it works a treat.
If I have say 40 live aircraft in my flights, I am able to immediately see which I've never seen before
Pm me if anyone wants to know more