private void AddPushButton(RibbonPanel panel)
{
    PushButton pushButton = panel.AddItem(new PushButtonData("HelloWorld",
        "HelloWorld", @"D:\Sample\HelloWorld\bin\Debug\HelloWorld.dll", "HelloWorld.CsHelloWorld")) as PushButton;

    // Set ToolTip and contextual help
    pushButton.ToolTip = "Say Hello World";
    ContextualHelp contextHelp = new ContextualHelp(ContextualHelpType.Url,
        "http://www.autodesk.com");
   pushButton.SetContextualHelp(contextHelp);

    // Set the large image shown on button
    pushButton.LargeImage = 
        new BitmapImage(new Uri(@"D:\Sample\HelloWorld\bin\Debug\39-Globe_32x32.png"));
}

Private Sub AddPushButton(panel As RibbonPanel)
   Dim pushButton As PushButton = TryCast(panel.AddItem(New PushButtonData("HelloWorld", "HelloWorld", "D:\Sample\HelloWorld\bin\Debug\HelloWorld.dll", "HelloWorld.CsHelloWorld")), PushButton)

   ' Set ToolTip and contextual help
   pushButton.ToolTip = "Say Hello World"
   Dim contextHelp As New ContextualHelp(ContextualHelpType.Url, "http://www.autodesk.com")
   pushButton.SetContextualHelp(contextHelp)

   ' Set the large image shown on button
   pushButton.LargeImage = New BitmapImage(New Uri("D:\Sample\HelloWorld\bin\Debug\39-Globe_32x32.png"))
End Sub