mixed texture able to control the opacity through script

So I need to create a mix texture of two images, yet i need to control each one's alpha value in the run time, I found this code in the forum

  Shader "Unlit/MixTextures" {
          Properties {
            _MainTex ("Main Base(RGB) Alpha(A)", 2D) = "white" {}
            _MainTex2 ("Main2 Base(RGB) Alpha(A)", 2D) = "white" {}
          }
          SubShader {
              Tags{"Queue"="Transparent"}
      
              Pass{
                  Lighting Off
                  SetTexture [_MainTex] {
                      combine texture, texture
                  }
              }
      
              Pass{
                  Blend DstColor Zero 
                  Lighting Off
                  SetTexture [_MainTex2] {
                      combine texture, texture
                  }
             }
          } 
          Fallback "Diffuse"
      }

Yet could anyone please tell me how do I access _mainTex and _MainTex2 through c# independently?