I was trying to achive the same object, i.e. have an object as the source of the light .I fail, and i think its not possible to do in poser. The closest effect i was able to get is adding high ambient value to the fake light, and have a gether node plugged into the surrounding material's alternate diffuse node. Then use a dark light, and tadaaam. But still, thats not what you or me are looking for, thats just a fake glow effect..