Even if you ask friendly, nobody will most probably sit down and write code for you for free. These forums are intended to point people towards the needed resources, so that they get the tools at hand to write their own code. Only when someone has already made the effort to write code and it has a few reproducible problems, others might jump in and help with debugging.
And here is the first hint: The Teensyduino Software comes with an ADC library which allows to achieve everything you want. Take the time to play with the example sketches until you understand enough to modify them to fit your needs.