Scroll Bar

I have a chat window and i want it to display the last messages from the players at the bottom of the conversation. The problem is that i have managed to do that but window won't go automatically to the bottom of the conversation unless i scroll it there otherwise it remains at the top of the conversation. Does anyone know how I can make it do that automatically?Than you. This is the code that i use for the chat windows

 function ChatWindow(id : int)
 {
     var s : String="";
     var ms : message;
     GUILayout.BeginVertical();
     _chatScrollVector2 = GUILayout.BeginScrollView(_chatScrollVector2, InvisibleStyle, InvisibleStyle);
 
     for(i=0;i<= allText.length-1;i++ )
     {
         ms = allText[i];
         newskin.customStyles[2].normal.textColor = ms.messageColor;
         s = ms.getAllText();
         var dbgstr : UnityEngine.Color = newskin.customStyles[2].normal.textColor;
         GUILayout.Label(""+s, newskin.customStyles[2]);
     }
     GUILayout.EndScrollView();    
     GUILayout.EndVertical();
 }