VBA : Number the slide if they are visible
<p>I have a powerpoint presentation with hidden slides.</p>

<p>I want to number only the visible slides.</p>

<p>I got this code :</p>

<pre><code>Sub Numerotation()
Dim x As Integer
Dim diapo As Slide
For Each diapo In ActivePresentation.Slides
  If diapo.SlideShowTransition.Hidden = False Then
    x = x + 1
    diapo.HeadersFooters.Footer.Text = x
  Else
    diapo.HeadersFooters.Footer.Text = ""
  End If
Next
End Sub
</code></pre>

<p>I got this error : </p>

<pre><code>Execution Error : '-2147188160 (80048240)':
HeaderFooter (unknown member) : Invalid request
</code></pre>

<p>I don't understand why vba doesn't recognise the HeaderFooter member (<a href="https://msdn.microsoft.com/en-us/library/office/ff745540.aspx" rel="nofollow">here is what MSDN says</a>)</p>

<p>Can you help me figure out what seems to be wrong?</p>