Switch from GUI button to toggle key

I have this script that's works fine currently although I want to press the "t" key instead of a GUI button toggleing the chat script to be visible.How can I change the toggle of the chat box from being toggled from a GUI button to being toggled with the "t" key?

Script:

 var skin : GUISkin;
 var showChat = false;
 private var inputField = "";
 private var display = true;
 private var entries = ArrayList();
 private var scrollPosition : Vector2;
 
 private var window = Rect(50, 50,700, 400);
 
 class ChatEntry
 {
     var sender = "";
     var text = "";    
     var mine = true;
 }
 
 function CloseChatWindow ()
 {
     showChat = false;
     inputField = "";
     entries = new ArrayList();
 }
 
 function FocusControl ()
 {
     // We can't select it immediately because the control might not have been drawn yet.
     // Thus it is not known to the system!
     yield;
     yield;
     yield;
     GUI.FocusControl("Chat input field");
 }
 
 function OnGUI ()
 {
     GUI.skin = skin;
     
     //if (GUILayout.Button(showChat ? "Hide Chat" : "Display Chat"))
     if (GUI.Button(new Rect(Screen.width-100, Screen.height-30, 90, 20), showChat ? "Hide Chat" : "Display Chat"))
     
     {
         // Focus first element
         if (showChat)
         {    
             CloseChatWindow ();
         }
         else
         {
             showChat = true;
             FocusControl();
         }
     }
     
     if (showChat)
         window = GUI.Window (1, window, GlobalChatWindow, "Chat");
 }
 
 function GlobalChatWindow (id : int) {
     
     var closeButtonStyle = GUI.skin.GetStyle("close_button");
     if (GUI.Button(Rect (4, 4, closeButtonStyle.normal.background.width, closeButtonStyle.normal.background.height), "", "close_button"))
     {
         CloseChatWindow();
     }
     
     // Begin a scroll view. All rects are calculated automatically - 
     // it will use up any available screen space and make sure contents flow correctly.
     // This is kept small with the last two parameters to force scrollbars to appear.
     scrollPosition = GUILayout.BeginScrollView (scrollPosition);
 
     for (var entry : ChatEntry in entries)
     {
         GUILayout.BeginHorizontal();
         if (!entry.mine)
         {
             GUILayout.FlexibleSpace ();
             GUILayout.Label (entry.text, "chat_rightaligned");
         }
         else
         {
             GUILayout.Label (entry.text, "chat_leftaligned");
             GUILayout.FlexibleSpace ();
         }
         
         GUILayout.EndHorizontal();
         GUILayout.Space(3);
         
     }
     // End the scrollview we began above.
     GUILayout.EndScrollView ();
     
     if (Event.current.type == EventType.keyDown && Event.current.character == "\n" && inputField.Length > 0)
     {
         //@TODO: This should be dependent on who actually sent the message
         //var mine = entries.Count % 2 == 0;
         ApplyGlobalChatText(inputField, 1);
         networkView.RPC("ApplyGlobalChatText", RPCMode.Others, inputField, 0);
         inputField = "";
     }
     GUI.SetNextControlName("Chat input field");
     inputField = GUILayout.TextField(inputField);
     
     GUI.DragWindow();
 }
 
 @RPC
 function ApplyGlobalChatText (str : String, mine : int)
 {
     var entry = new ChatEntry();
     entry.sender = "Not implemented";
     entry.text = str;
     if (mine == 1) entry.mine = true;
     else entry.mine = false;
 
     entries.Add(entry);
     
     if (entries.Count > 50)
         entries.RemoveAt(0);
         
     scrollPosition.y = 1000000;    
 }
 
 function Update (){
 if(Input.GetKeyDown(KeyCode.Return)){
 
 showChat = true;
 
 }
 
 }