Material ID on a submaterial level

As of now, if I have a blendmaterial with a few submaterials and attach a material ID to the submats, they don’t get a multimatte when I render. Would this be possible?

What about this thread : http://www.chaosgroup.com/forums/vbulletin/showthread.php?67401-Vray-quot-material-select-render-element-quot-output-material-ID-or-flat-color&highlight=material ?