Adding Materials???

Does anyone know how to add new materials to AutoCAD's render.mli file? (I know how to do it in a roundabout way, but that is only by modifying an existing material with another *.tga file. But I don't want to do that. I want to actually add new *.tga files to render.mli.)

Ok I figured it out! Here's what I did. In the materials libray, I imported a *.tga file from render.mli to my current drawing, clicked on "modify" and changed the material name, deleted the current *.tga file that was there, and then replaced with the one I wanted. Then I resaved the new ender.mli file. It was A LOT easier than what this guy did here.