ignore a shader pass under some conditions

I have an outline shader that has 2 passes, thus for every game object i have 2 draw calls.

The first call is used only for outline purposes, but my object is not always outlined, so i would wish to enable that pass only when a certain variable is greater than 0. Is it possible?

Here is the shader:

 Shader "Outlined/Silhouetted Diffuse" {
     Properties {
         _Color ("Main Color", Color) = (.5,.5,.5,1)
         _OutlineColor ("Outline Color", Color) = (0,0,0,1)
         _Outline ("Outline width", Range (0.0, 0.3)) = 0
         _MainTex ("Base (RGB)", 2D) = "white" { }
     }
     
     SubShader {
         Tags { "Queue" = "Transparent" }
 
         Pass {
             Name "OUTLINE"
             Tags { "LightMode" = "Always" }
             Cull Back
             ZWrite Off
             ZTest Always
             ColorMask RGB
         
             CGPROGRAM
             #pragma only_renderers gles opengl
             #pragma vertex vert
             #pragma fragment frag
             
             #include "UnityCG.cginc"
             
             struct appdata {
                 half4 vertex : POSITION;
                 half3 normal : NORMAL;
             };
             
             struct v2f {
                 half4 pos : POSITION;
                 half4 color : COLOR;
             };
             
             uniform half _Outline;
             uniform half4 _OutlineColor;
             
             v2f vert(appdata v) {
                 v2f o;
                 
                 o.pos = mul(UNITY_MATRIX_MVP, v.vertex);
             
                 half3 norm   = mul ((half3x3)UNITY_MATRIX_IT_MV, v.normal);
                 half2 offset = TransformViewToProjection(norm.xy);
             
                 o.pos.xy += offset * _Outline; 
                 o.color = _OutlineColor;
                 return o;
             }
             
             half4 frag(v2f i) :COLOR {
                 return i.color;
             }
             ENDCG
         }
 
         Pass {
             Name "BASE"
             ZWrite On
             ZTest LEqual
             Blend SrcAlpha OneMinusSrcAlpha
             Material {
                 //Diffuse [_Color]
                 //Ambient [_Color]
             }
             Lighting On
             SetTexture [_MainTex] {
                 //ConstantColor [_Color]
                 //Combine texture * constant
             }
         }
     }
     
     Fallback "Diffuse"
 }

When "_Outline" is equal to 0, i would like to ignore the first PASS. Is this possible?