I need to use custom keywords in my cg shader, but so far I can't get them working. I looked at the Water4 shader and scripts - since it uses custom keywords - and tried to setup my files the same way, but so far I can't get it to work.

Here's my shader( my custom keyword is in the "surf" function ):

Shader "SRShaders/Bumped Specular (1 Directional Light)" {
Properties {
    _Shininess ("Shininess", Range (0.03, 1)) = 0.078125
    _MainTex ("Base (RGB) Gloss (A)", 2D) = "white" {}
    _BumpMap ("Normalmap", 2D) = "bump" {}
}
SubShader { 
    Tags { "RenderType"="Opaque" }
    LOD 250

CGPROGRAM
#pragma surface surf MobileBlinnPhong exclude_path:prepass nolightmap noforwardadd halfasview novertexlights


inline fixed4 LightingMobileBlinnPhong (SurfaceOutput s, fixed3 lightDir, fixed3 halfDir, fixed atten)
{
    fixed diff = max (0, dot (s.Normal, lightDir));
    fixed nh = max (0, dot (s.Normal, halfDir));
    fixed spec = pow (nh, s.Specular*128) * s.Gloss;

    fixed4 c;
    c.rgb = (s.Albedo * _LightColor0.rgb * diff + _LightColor0.rgb * spec) * (atten*2);
    c.a = 0.0;
    return c;
}

sampler2D _MainTex;
sampler2D _BumpMap;
half _Shininess;


struct Input {
    float2 uv_MainTex;
};

void surf (Input IN, inout SurfaceOutput o) {
    fixed4 tex = tex2D(_MainTex, IN.uv_MainTex);
    o.Albedo = tex.rgb;

    #ifdef IS_SIMPLE  // My custom keyword
    o.Albedo *= 4;
    #endif

    o.Gloss = tex.a;
    o.Alpha = tex.a;
    o.Specular = _Shininess;
    o.Normal = UnpackNormal (tex2D(_BumpMap, IN.uv_MainTex));
}
ENDCG
}

FallBack "Mobile/VertexLit"
}

And here's my script:

using UnityEngine;
using System.Collections;

[ExecuteInEditMode]
public class ShaderManager : MonoBehaviour {

    // Store the camera
    public Camera cam;
    public Texture2D tex;


    // Before the object gets rendered
    public void OnWillRenderObject ( ) {

        cam = Camera.current;

        if( !cam )
            return;

        Shader shader = renderer.sharedMaterial.shader;
    }

    void OnEnable() {

        Shader.EnableKeyword("IS_SIMPLE"); // My custom keyword
    }

    void OnDisable() {

        Shader.DisableKeyword("IS_SIMPLE"); // My custom keyword
    }
}

I should mention that the script is NOT in the same folder as the shader, and that I am not using Unity Pro. I'm using Unity 3.5 iPhone basic.

I can't find any documentation on this issue, so I need a shader guru's help hehe :)
Thanks in advance!
Stephane