need sioc script for VSI indicator (stepper motor )

HI People

I have a stepper that works through sioc an The sim, but it does not stop when it reach 6000 ft/min (max on instrument ) . It tend to make full 360 rotations..how do i write the script that if i climb, the needle goes positve and stop at 180 degrees from 0 point and visa versa. I Use the Offset $02c8 , there is another Offset $0842

Thanks Marnus