Not very easy, because:
- The arrival gate doesn't mean anything, if no destination airport is also specified, since an arrival gate can be chosen by users even before landing, and they can change their mind, and either select a different gate or even a different airport altogether.
- Just a number on an L: var (which can only store numbers) won't help identifying the gate, unless the 3rd party app would be able to BOTH identify the AFCAD in use AND being able to OPEN it, decode it, so it could obtain a list of gates, and convert it into a gate "index" to pass to GSX.
Very complex, and with so many things that could go wrong.