Adding transparency to a 2 texture blending shader...noobie.

Im new to messing with shaders and pieced this one together, but now im having trouble adding translucency to this....How would I get the 2 textures to be blendable but also have a slider or something that makes the blended outcome translucent?

  Shader "Custom/My ToonShader Test1" {
 Properties {
 _Lookup ("BRDF Color Ramp", 2D) = "gray" {}
 _MainTex ("Texture", 2D) = "white" {}
 _Detail ("Texture", 2D) = "white" {}
 _Blend ( "Blend", Range ( 0, 1 ) ) = 0.5
 _RimPower ("Rim Power", Float) = 1.4
 _RimColor ("Rim Color (RGB) + Intensity (A)", Color) = (0.0,0.0,0.0,1.0)
 _SColor ("Shadow Color", Color) = (0.0,0.0,0.0,1)
 _LColor ("Highlight Color", Color) = (0.5,0.5,0.5,1)
 }
 SubShader {
 Tags { "RenderType"="Opaque" }
 LOD 200
 Pass
 {
 SetTexture[_MainTex]
 SetTexture[_Detail]
 {
 ConstantColor ( 0, 0, 0, [_Blend] )
 Combine texture Lerp( constant ) previous
 }
 }
 CGPROGRAM
 #pragma surface surf Lookup
 sampler2D _MainTex;
 sampler2D _Lookup;
 float _Blend;
 sampler2D _Detail;
 float4 _LColor;
 float4 _SColor;
 float _RimPower;
 float4 _RimColor;
 struct Input
 {
 float2 uv_MainTex;
 float4 screenPos;
 float2 uv_Detail;
 float3 pos : POSITION0;
 float3 viewDir;
 };
 half4 LightingLookup (SurfaceOutput s, half3 lightDir, half3 viewDir, half atten)
 {
 float NdotL = dot(s.Normal, lightDir);
 float NdotV = dot(s.Normal, viewDir);
 float2 lookupUV = float2(NdotV*.8, NdotL * 0.5 + 0.5);
 float3 exitRadiance = tex2D(_Lookup, lookupUV).rgb;
 float4 c;
 c.a = s.Alpha;
 #ifndef USING_DIRECTIONAL_LIGHT
 lightDir = normalize(lightDir);
 #endif
 half d = dot (s.Normal, lightDir)*0.5 + 0.5;
 half3 ramp = tex2D(_Lookup, float2(d,d)).rgb;
 ramp = lerp(_SColor, _LColor, ramp);
 c.rgb = s.Albedo * _LightColor0.rgb * ramp * (exitRadiance * (atten * 2));
 return c;
 }
 void surf (Input IN, inout SurfaceOutput o)
 {
 float2 screenUV = IN.screenPos.xy / IN.screenPos.w;
 screenUV *= float2(1,1);
 half4 mainTex = tex2D (_MainTex, IN.uv_MainTex);
 o.Albedo = mainTex.rgb;
 o.Alpha = mainTex.a;
 fixed4 t1 = tex2D( _MainTex, IN.uv_MainTex);
 fixed4 t2 = tex2D( _Detail, screenUV)*2;
 o.Albedo = lerp( t1, t2, _Blend);
 //Rim Outline
 half rim = saturate( dot(normalize(IN.viewDir), o.Normal) );
 o.Albedo *= 1.0f - (step(rim, _RimPower) * (1.0f-_RimColor) * _RimColor.a);
 }
 ENDCG
 }
 Fallback "Diffuse"
 }