Opacity of textured object

I am currently working with a textured object. I have followed a few suggestions, but the following code will not work

  void Update ()
  {
        if (triggered)
         {
              if (objectToTransparent.renderer.material.color.a > 0)
              {
                  Color color = objectToTransparent.renderer.material.color;
                  color.a =- speed;
                  objectToTransparent.renderer.material.color = color;
              }
         }
}

I am trying to make something slowly more and more transparent with every update frame at a certain speed. This object however is textured and is immune to this… aghorithm. I need to make it fade into completely transperancy and this method is not working. Has anyone had to solve this issue before?

Make sure you are using a transparent shader or it will have no effect.