Normal Dot Light

I''m trying to do something very simple...calculate the dot product between a normal map and a light direction. When i change the direction of the light the result doesn''t change. In TEXTURE0 i pass the normal map, CONSTANT_COLOR0 is the light direction, and PRIMARY_COLOR is the ambient light. I use 1 general combiner for the dot product. The sum between the dot product and the ambient light is done in the final combiner. What may be the problem???. Thanks in advance. HellRaiZer. Ps.If you need code to understand what i''m trying to do ,i''ll post it.