title: Ribbon.InvalidateControl not working on PPT 2010
body: <p>I have a an add-in within the Insert Ribbon of PPT 2010. Basically what I want to do is to make a selection in a combo box, then run a macro, then set the combo box to blank. Unfortunately I´v been unable to clear the selection. </p>
  
  <p>I have searched all over the web with various methods and nothing helps. Hope someone can help.</p>
  
  <p>My XML</p>
  
  <pre><code>&lt;customUI xmlns="http://schemas.microsoft.com/office/2006/01/customui" onLoad="VirtusInitialize"&gt;
  &lt;ribbon&gt;
  &lt;tabs&gt;
  &lt;tab idMso="TabInsert"&gt;
  &lt;group id="CustomGroup1" label="Sticker"&gt;
  &lt;box id="box1" boxStyle="horizontal"&gt;
      &lt;comboBox id="ddlItem" label="STICKER 1" onChange="Sticker1"&gt;
        &lt;item id="BU" label="BACK UP" /&gt;
      &lt;/comboBox&gt;
  &lt;/box&gt;
  &lt;/group&gt;
  &lt;/tab&gt;
  &lt;/tabs&gt;
  &lt;/ribbon&gt;
  &lt;/customUI&gt;
  </code></pre>
  
  <p>VBA code:</p>
  
  <pre><code>Private MyRibbonV As IRibbonUI
  
  
  Public Sub VirtusInitialize(ByVal ribbon As Office.IRibbonUI)
    Set MyRibbonV = ribbon
  End Sub
  
  Sub Sticker1(ByVal control As IRibbonControl, text As String)
   'do stuff
    MyRibbonV.InvalidateControl ("ddlItem")
  End Sub
  </code></pre>