Speech in PowerPoint (VBA)

I want to be able to make PowerPoint speak, say something.

I tried this code to make PP speak:

Private Sub CommandButton1_Click()
Application.Speech.Speak "Hello World"
End Sub

But the code doesn't work, it doesn't exists. What can I do, which is the right code?

It says:

Compile Error Method or Data member not found.

Sorry for any error on my question.

Solution

The reason it's not working is that there's no Application.Speech property/method in the PPT object model. Somewhere or other I've seen code that invokes Excel to do the lifting but here's an answer from John Wilson of PPT Alchemy that seems more direct:

There is a page on our site about talking message boxes http://www.pptalchemy.co.uk/PowerPoint_speech.html

It could be easily modified to speak the text in a shape in Slide Show mode.

Sub speak(oshp As Shape)
  Dim strSpeak As String
  Dim SAPIObj As Object
  Set SAPIObj = CreateObject("SAPI.SPvoice")
  SAPIObj.Rate = -2
  If oshp.HasTextFrame Then
    If oshp.TextFrame.HasText Then
      strSpeak = oshp.TextFrame.TextRange.Text
    End If
  End If

  SAPIObj.speak "<pitch middle='-15'>" & strSpeak

End Sub

If you don't need to pick up the text from a particular shape, a modification along these lines should do it:

Sub SayThisAloud(sText as String)

  Dim SAPIObj As Object
  Set SAPIObj = CreateObject("SAPI.SPvoice")
  SAPIObj.Rate = -2

  SAPIObj.speak "<pitch middle='-15'>" & sText

End Sub