AutoCAD Architecture :: Unable To Use Object / Material Combination As Negative

Im trying to create a material for glass balustrade that will elevate and show outline but not block what is behind.  Useful for shr screens (show tiling, taps etc) balustrade for balconies, stairs etc.

I have balustrade I'm working on now using a railing object. There are no posts at all and I'm using dynamic posts with a nothing material to cut up the guardrail material into pieces.  So need the posts to disappear but stil cut the glass into sections.  Also in elevation, need to see the glass outline but also to show what's behind. Normal glass in elevation rightly blocks what's behind (inside).

There is a problem with how materials operate. You are unable to use an object/material combination as a negative.  For e.g. assigning my posts above a material that has 3d body turned off negates it impacting the glass (ie no longer cuts) so I have to 'see' the gaps otherwise the glass goes straight thru.  The post has to be directly inline with the glass to cut (fair enough) but turning the 'gap' material 3D body display off and the railing def no longer sees the post cutting the glass just because 3d body is turned off in the material display. (not sure why these have to be linked.  If glass has frame (shr screen) then it's ok. just turn off glass but if in the case of glass balustrade you need to be able to do it.

Im thinking maybe using another object rather than railing, like a curtain wall and having a very small width frame using normal glass material that will elevate and another glass material that will disappear.