Excel VSTO Application_WindowActivate
<p>I'm developing Excel addin using VSTO and faced strange error when i switch beetwen windows - Application_WindowActivate event isn't fired. It is working only when i switch between excel windows not when i switch beetwen office window and  excel window for example. Event WindowActivate is working perfectly in my word addin. </p>

<p>Any Help ?</p>

<pre><code>private void ThisAddIn_Startup(object sender, System.EventArgs e)
    {
        this.Application.WindowActivate += Application_WindowActivate;
    }

 private void Application_WindowActivate(Microsoft.Office.Interop.Excel.Workbook Wb, Microsoft.Office.Interop.Excel.Window Wn)
    {
        Refreshribbon();
    }
</code></pre>