Thank you, I appreciate the time you spent on this.
I did this , previously, yes and its a very good cheat.
The reason I asked originaly was the client sited a stain glass effect from the glass, but ry are to boxes with light on the inside and the colour of the glass pumping out from them on the floor.
Like the attahed, it's for an installation no natural light coming in.
But what you have suggested might do the trick locally to each side.
There is always a way round, and always many ways.
Thank you again.
Phil