I use the same mechanic when I look at a an item but I want to detect if it has a placeholder (which is another mesh) I want to attach items to. The first trace detects if I trace a placeholder, if true I set it to a bool, that is all. From there I continue with my normal trace, the one with all the scripting.
Something like this (sorry for the separate images)
That way the trace can ignore the first mesh (the 3D Structure) and trace the boxes once they have moved behind it.