Shader - Using Multiple Pass for different shader target

Hi Guys, I had a little problem when writing my own vertex/fragment shader.

at first, my shader requires at least SM (Shader Model) 3.0, then I want to create simpler one so it can targeting lower SM (2.0). so I'm trying to do something like this :

 SubShader {
 
    Pass {
    CGPROGRAM
    #pragma target 2.0
 
    ...
 
    ENDCG
    }
    Pass {
    CGPROGRAM
    #pragma target 3.0
 
    ...
 
    ENDCG
    }
 }

when I set graphic emulation to Shader Model 3, it works. However, it doesn't work when setting graphic emulation to Shader Model 2. How to make this thing work?