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 circle3) "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 circleIm 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.

sorry, forgot to attach a dwg file...http://i46.tinypic.com/10d8wwn.jpguploads/35063/duct_section.dwgIm using AC 2012