private void AddElem(Microsoft.Office.Interop.Word.Document MyDoc)
    {
        //  Start adding elem
        Microsoft.Office.Interop.Word.InlineShape[] cx = new Microsoft.Office.Interop.Word.InlineShape[1];
        MSComctlLib.Toolbar[] barr = new MSComctlLib.Toolbar[1];
        string str = "Hello";

        cx[0] = MyDoc.InlineShapes.AddOLEControl("MSComctlLib.Toolbar");
        barr[0] = ((MSComctlLib.Toolbar)cx[0].OLEFormat.Object);
        barr[0].Buttons.Add().ToolTipText = str;
    }

barr[0].Buttons.Add().ToolTipText = str;