how to add bumpmap to MirrorReflection as surface shader

Hi,

i have rewritten the MirrorReflection2 shader as a surface shader, but i can't figure out how to add bumpmap distortion to the reflection... Here's my surface code so far:

 void surf (Input IN, inout SurfaceOutput o) {
     fixed2 screenUV = (IN.screenPos.xy) / (IN.screenPos.w);
     fixed3 nor = UnpackNormal (tex2D(_BumpMap, IN.uv_BumpMap));
     fixed4 tex = tex2D (_MainTex, IN.uv_MainTex);
     fixed4 refl = tex2D (_ReflectionTex, screenUV);
     o.Albedo = tex.rgb *_Color.rgb;
     o.Normal = nor.rgb;
     o.Emission = refl.rgb;
 }

i think i should use something like WorldReflectionVector to get the normals and then apply reflections, but i hane no idea how to do this in a surface shader... any idea?