I'm having trouble on figuring out how to scroll a texture in a surface shader. What I'm trying to make is a surface shader that has both rim lighting (which is implemented) and has a texture which scrolls around the object it's on. This is my shader up to now:

 Shader "Custom/StarShader" {
     Properties{
     _Color("Color", Color) = (1,1,1,1)
     _MainTex("Texture", 2D) = "white" {}
     _SubTex("Texture", 2D) = "white" {}
     _RimColor("Rim Color", Color) = (0.26,0.19,0.16,0.0)
     _RimPower("Rim Power", Range(0.1,2.0)) = 3.0
     _ScrollXSpeed("X", Range(0,10)) = 2
     _ScrollYSpeed("Y", Range(0,10)) = 3
 
     }
         SubShader{
         Tags{ "RenderType" = "Opaque" }
         CGPROGRAM
 #pragma surface surf Lambert
     struct Input {
         float2 uv_MainTex;
         float2 uv_SubTex;
         float3 viewDir;
         fixed _ScrollXSpeed;
         fixed _ScrollYSpeed;
     };
     sampler2D _MainTex;
     sampler2D _SubTex;
     float4 _RimColor;
     float _RimPower;
     fixed4 _Color;
 
     void surf(Input IN, inout SurfaceOutput o) {
         fixed2 scrolledUV = IN.uv_MainTex;
 
         fixed xScrollValue = _ScrollXSpeed * _Time;
         fixed yScrollValue = _ScrollYSpeed * _Time;
 
         scrolledUV += fixed2(xScrollValue, yScrollValue);
         half4 c = tex2D(_MainTex, scrolledUV);
 
         o.Albedo = tex2D(_MainTex, IN.uv_MainTex).rgb;
         o.Albedo += c.rbg;
 
         half rim = 1.0 - saturate(dot(normalize(IN.viewDir), o.Normal));
         o.Emission = _RimColor.rgb * pow(rim, _RimPower);
     }
     ENDCG
     }
         Fallback "Diffuse"
 }

I simply want to find a way on how to scroll the texture around the object via a shader. I'm getting multiple "Undefined variable" errors trying it this way.