Blending Lightmaps and Dynamic Texture Shadows in HLSL

I’m using Gile[s] as my lightmapper and my engine can execute HLSL scripts with DirectX 9.

I would like to accomplish something like this for performance reasons. I was told that this technique can only be done by shaders.

Someone has provided me with a quick code example and starting code but it is still far from being implemented.

lightmapColor*=shadowmapValue;
colorIntensity = (lightmapColor.r+lightmapColor.g+lightmapColor.b)/3.0;
lightCol = (1-colorIntensity)*ambient+(colorIntensity)*lightmapColor;

Not sure if it is applicable in my engine so I am looking for some guidance and perhaps some basic hlsl code to accomplish this. My lightmap texture uses the UV2 Channel if it helps. Thanks.