Autotrim System (Airbus): How?

I would like make the autotrim system, as the same in real AIRBUS but the system have any features writing below:*Autotrim not avaliable in the ground.*Autotrim resets to ZERO position when the aircraft landing.*Autotrim only avaible after takeoff.Example: With de autopilot OFF, the pilot initialize an descent profile (2500 V/S). If the pilot release sidestick, the autotrim keeps 2500 V/S. The same for climbs.Its possible? How to make an autorim system? Anybody here know?This is part of a project that it aims at to improve Airbus PSS. Who to know program, please, writes code or makes the archive and send me for email.Best regards!Alan/Brazil