I'm sorry I don't know if that can be done in Poser. It will depend on the render engine and scope you have for using extreme values in the material channels. Internally Bryce operates at 48 bit precision in high dynamic range linear colour space and is a biased render engine, which means there is a lot of opportunity to produce physically impossible materials. If Poser is similar then there is a good chance you can find a way to achieve this effect also. But not being a Poser users, I can't really offer you more than that.