Change GUI.Button Texture on runtime

I want to change the texture of a button depending of the value of a variable:

             StartCoroutine(DoublePrize()); 
             if(doubleOptionA)
             {
                 textureA = optionAActive;
                 textureB = optionB;
             }
             else
             {
                 textureA = optionA;
                 textureB = optionBActive;
             }
 
             if(GUI.Button(optionAPos,textureA)) { doubleTries--; }
             if(GUI.Button(optionBPos,textureB)) { doubleTries--; }

That's is inside OnGUI. Then I have the function DoublePrize with this code:

 IEnumerator DoublePrize()
 {        
     while(doubleTries > 0)
     {            
         doubleOptionA = !doubleOptionA;
         yield return new WaitForSeconds(1f);
     }

 }

I use Debug.Log to see if doubleOptionA is changing (I use it both on OnGUI and on DoublePrize()) and is changing good! What not is changing is the textures! I see always textureA = optionA and textureB = optionBActive. What I'm doing wrong?

EDIT: I was calling DoublePrize() from GUI! So the variable doubleOptionA was switching from true to false so fast that it seems to be always in the same state! I solve that an the problem is gone! :)