Hi,
Im trying to create ventilation duct section using dynamic block. Duct section consist on:
1) outside circle (dashed) - it stands for insulation od the duct.
2) concentric inside circle
3) "moon" inside.

I would like to be able to manipulate:
1) diameter of the outside circle (dashed)
2) diameter of inside circle
and I would like the "moon" to be scaled while Im changing diameter of inside circle

Im trying to do it using constraints and using scale parameter. Both blocks you can see in attached drawing. As you can see I cannot achieve my goal.

Any help will be apriciated.