Is it possible to add an outline using standard surface shader?

So I've only started messing around with shaders and have managed to write the shader below to do a few things like blend two textures, add emission etc. - it works

I've been looking around for some info on if/how i may be able to add an outline using the same shader. I've come across a few examples but they all seem to be using emission to do this and it does not give me the effect I desire. I'm looking for a black outline i can adjust the width of using a slider.

is this at all possible with a surface shader or only with a vertex shader?

(I'm using a surface shader because I need it to react to lighting)

Go gentle if I've made any noob errors

Code (CSharp):

1. Shader "Dreemlabs/TextureBlendByUV" {
2.         Properties {
3.             _Color ("Color", Color) = (1,1,1,1)
4.             _Blend ("Texture Blend", Range(0,1)) = 0.0
5.             _MainTex ("Albedo (RGB)", 2D) = "white" {}
6.             _MainTex2 ("Albedo 2 (RGB)", 2D) = "white" {}
7.            
8.             _Emissive("Emission", 2D) = "black" {}
9.             _EmissiveColor("Emission Color", Color) = (1,1,1,1)
10.             _EmissiveIntensity("Emission Intensity", Range(0,1) ) = 1
11.  
12.             _Glossiness ("Smoothness", Range(0,1)) = 0.5
13.             _Metallic ("Metallic", Range(0,1)) = 0.0
14.         }
15.  
16.         SubShader {
17.             Tags { "RenderType"="Opaque" }
18.             LOD 200
19.        
20.             CGPROGRAM
21.                 // Physically based Standard lighting model, and enable shadows on all light types
22.                 #pragma surface surf Standard fullforwardshadows
23.        
24.                 // Use shader model 3.0 target, to get nicer looking lighting
25.                 #pragma target 3.0
26.        
27.                 sampler2D _MainTex;
28.                 sampler2D _MainTex2;
29.  
30.                 sampler2D _Emissive;
31.        
32.                 struct Input {
33.                     float2 uv_MainTex;
34.                     float2 uv2_MainTex2;
35.  
36.                     float2 uv_Emissive;
37.                 };
38.        
39.                 half _Blend;
40.                 half _Glossiness;
41.                 half _Metallic;
42.                 fixed4 _Color;
43.  
44.                 float4 _EmissiveColor;
45.                 float _EmissiveIntensity;
46.        
47.                 void surf (Input IN, inout SurfaceOutputStandard o) {
48.                     fixed4 c = lerp (tex2D (_MainTex, IN.uv_MainTex), tex2D (_MainTex2, IN.uv2_MainTex2), _Blend) * tex2D (_MainTex, IN.uv_MainTex);
49.                     o.Albedo = c.rgb;
50.                     o.Alpha = tex2D (_MainTex, IN.uv_MainTex);
51.  
52.                     float4 Tex2D1=tex2D(_Emissive,(IN.uv_Emissive.xyxy).xy);
53.                     float4 Multiply0=Tex2D1 * _Color.xyxy;
54.                     float4 Multiply2=Multiply0 * _EmissiveIntensity.xxxx  * _EmissiveColor ;
55.                     o.Emission = Multiply2;
56.  
57.                     o.Metallic = _Metallic;
58.                     o.Smoothness = _Glossiness;
59.                 }
60.             ENDCG
61.         }
62.         FallBack "Diffuse"
63.     }