Texture height based on it width.

Hi, I have a GUITexture which content changes time by time. All texture defined have the same width, but the height may change. Until now, I have something like this:

 void Start (){
     messageSize = new Vector2(Screen.width/3, Screen.height/5);        
     messageGO = new GameObject();
     messageGO.transform.position = Vector3.zero;
     messageGO.transform.localScale = Vector3.zero;
     messageGUI = messageGO.AddComponent<GUITexture>();
     messageGUI.name = "Message";
 }


 void Update(){    
     if(displayMessage){
        timer += Time.deltaTime;
         if(timer <= time){
            messageGUI.enabled = true;
            messageGUI.texture = message;
            messageGUI.pixelInset = new Rect(position.x,position.y,messageSize.x,  
                                    messageSize.y);                                                          
         }
         else{
             messageGUI.enabled = false;    
             displayMessage = false;
             timer = 0f;
             currentMessage ++;
         }
     }
 } 

So, I was wondering if there is a way to make this messageSize.y adjusts dynamically. Something like we do in HTML, passing width = messageSize.x and messageSize.y = '*'.

What I have so far are fix messageSize. I would like that the messageSize.y change to have the necessary size, like we can do in HTML with the parameter height = '*'.