Using another material as input to material nodes is normally the feature of Node Groups.
Works well in the Blender Cycles. However, it somehow falls short in Cycles4D.
In Cycles4D, to be able to reference a node group as the input you need to:
1) Save it to an external file (.cyg)
2) Load it the external file back in.
In the Blender Cycles, you can opt not to save it. Basically, the node group lives within the scene and you can add it willingly.
Here's the kicker,
In Cycles4D, if you change something in the node group, you need to save it again and load it.
In Blender Cycles, if you change something, it propagates to other materials using the node group.
I'm not sure about C4D architecture but I know this was also possible in Vray4C4D. So I'm guessing, it's also possible in Cycles4D.
I'm just not sure how.
Is there a way around this?