Solar radiation though double glazing

Multiband

Hi everybody, I'm a beginner to cfx, so maybe my question is very easy to answer... I'm doing a solar collector, with solar radiation though a double glazing (they have all different domain, glass, air and then other solid materials after the double glazing). I read the tutorial 17, so I have done the solar radiation source, but now I have to set the boundary conditions of the glasses... I use MonteCarlo as Thermal Radiation Model. I read in this forum that I could set as thermal radiation between the glass and air "Conservative Interface Flux", use a gray spectral model for the air and a multiband spectral model for the glass(with two spectral bands those have the wavelengths in vacum from 0 to 2.7 micron and from 2.7 to 1000 micron). I haven't understood how do them... I would know if these steps are right and what else I have to do for the multiband.I have to set some CEL functions (if yes, which?) or to set something in the material properties for the different bands? Thank you very much