Self Lit, Alpha channel (global), Texture mapped to UV, Mask mapped to UV2

Shader4S.cg

Shader "Custom/Shader4S" {
Properties {
    _MainTex ("Texture", 2D) = "white" { }
    _Mask ("Mask", 2D) = "white" {}
    _Alpha ("Alpha", Range(0.0,1.0)) = 1.0
}
SubShader {
    Tags { Queue = Transparent }
    ZWrite Off
    Blend SrcAlpha OneMinusSrcAlpha
    Pass {
		BindChannels {
			Bind "Vertex", vertex
			Bind "texcoord", texcoord1
			Bind "texcoord1", texcoord0
		} 
    	SetTexture [_Mask] {combine texture}
        SetTexture[_MainTex] {
	        combine texture, previous * texture
	        constantColor(0,0,0,[_Alpha])
	        combine texture, previous * constant
	    }
	    
    }
}
}