Backface Transparent Diffuse Shader

Im totally new at Shaders, and i really understand only a bit, but i want one which shows me only the backfaces of an Object in a color i want with transparancy.

What i have till now is this. All works except the transparancy.

Shader "Show Insides" 
{
    Properties 
    {
        _Color ("Main Color", Color) = (1,1,1,0)
    }

    SubShader 
    {
        Pass 
        {
            Blend SrcAlpha OneMinusSrcAlpha
            Color [_Color]
            Cull Front
        }
    }
} 

Try putting this in there:

    Tags {"Queue" = "Transparent" }