How to change a value in custom shader through script, C#

Hi!

I´m using a shader that i found on the net, called "Blend 2 Textures" Here´s the shader:

 Shader "Blend 2 Textures" { 
 
 Properties {
     _Blend ("Blend", Range (0, 1) ) = 0.5 
     _MainTex ("Texture 1", 2D) = "" 
     _Texture2 ("Texture 2", 2D) = ""
 }
 
 SubShader {    
     Pass {
         SetTexture[_MainTex]
         SetTexture[_Texture2] { 
             ConstantColor (0,0,0, [_Blend]) 
             Combine texture Lerp(constant) previous
         }        
     }
 } 
 
 }

Im trying to use that Blend-value through a C#-script so that i can control the blending on the fly, but i haven´t had much success. i can get the blend value by using

 print(renderer.material.GetFloat("_Blend"));

but my problem starts from there. I just cant get my script to add or subtract anything to that exact value of Blend.

Any help is appreciated, thanks beforehand :)

I´ll add my latest failure here also, if its of any help

 public class Event_Planet : MonoBehaviour {
     
     public float blendersValue;
     public float blendValue; 
         
     void Start() {
         
         renderer.material.shader = Shader.Find("2TextureBlend");
            
     }
     void Update () {
 
         print(renderer.material.GetFloat("_Blend"));
         blendersValue = blendersValue + blendValue;
         
     }
 }