FS FORCE

my c172 is trimmed the trin gauge show 10. I push the trim -up button but I keep the joystik firmly in the same position as the force increase. the trim gauge show 40 . I still trim up but on my monitor I see the virtual yoke move to me and the c172 nose go up. the joystik is in the same position but in fsx the pitch change when the trim gauge show biggest setting.
Why??

If the virtual yoke is moving on the screen, then that means the joystick moved in your hand. I've done the same thing myself ... trying to keep the stick steady only to have the airplane pitch up or down. It's not easy to make trim changes and at the same time keep the joystick from moving.