Disable window in the scene

Here I have two window on the same screen.In first window I have placed a button and when i click that button the message will appear to be on 2nd window.Here is my code

void OnGUI() {
		windowRect0 = GUI.Window(0, windowRect0, DoMyWindow, "FIRST PAGE");
		windowRect1 = GUI.Window(1, windowRect1, DoMyWindows, "WELCOME PAGE");
	}
	void DoMyWindow(int windowID) {
		if (GUI.Button (new Rect (10, 20, 100, 20), "Hello World"))
			output= "error";			
					
	}
	void DoMyWindows(int windowID) {
		GUI.Label (new Rect (140, 92, 130, 500),output);

		
	}

When I click on the button in the 1st window,the first window should disappear and only the 2nd winodw should display.Can anybody help me?

private bool firstPage=true;
private bool welcomePage = false;

void OnGUI() {

    if(firstPage)
    {
        windowRect0 = GUI.Window(0, windowRect0, DoMyWindow, "FIRST PAGE");
    }

    if(welcomePage)
    {
        windowRect1 = GUI.Window(1, windowRect1, DoMyWindows, "WELCOME PAGE");
    }

     void DoMyWindow(int windowID) {
        if (GUI.Button (new Rect (10, 20, 100, 20), "Hello World"))
            {
               output= "error";
               firstPage = false;
               welcomePage = true;
            }          
 
    }

    void DoMyWindows(int windowID) {
        GUI.Label (new Rect (140, 92, 130, 500),output);

}