Esse código pode ajudar. Mas você precisa ter o gráfico colado no PowerPoint como um objeto OLE vinculado.
Option Explicit
Sub HyperLinkSearchReplace()
Dim oSl As Slide
Dim oSh As Shape
Dim sSearchFor As String
Dim sReplaceWith As String
sSearchFor = InputBox("What text should I search for?", "Search for ...")
If sSearchFor = "" Then
Exit Sub
End If
sReplaceWith = InputBox("What text should I replace it with" & vbCrLf _
& sSearchFor & vbCrLf _
& "with?", "Replace with ...")
If sReplaceWith = "" Then
Exit Sub
End If
On Error Resume Next
For Each oSl In ActivePresentation.Slides
For Each oSh In oSl.Shapes
If oSh.Type = msoLinkedOLEObject _
Or oSh.Type = msoMedia Then
oSh.LinkFormat.SourceFullName = _
Replace(oSh.LinkFormat.SourceFullName, _
sSearchFor, sReplaceWith)
End If
Next
Next ' slide
End Sub