OK, I used Universal g-code sender to move the z-axis by 12mm. It actually moved 56.169mm. Then I used your formula.
Current steps/mm was 188.947 which made the new steps/mm 83.602. Then I entered $122=83.602 in the machine's inspector console, and went to the carve of a piece. The result was that the start of the cut instead of being at x=1 and y=1, it moved to a spot about 12inches away from y start and 8 from x start, but when cutting, z still dropped about 1/4" per pass. I guess I'm lost and need help
Sorry for the bother, Doug