This example loops through all the shapes on all the slides in the active presentation and sets all linked Microsoft Excel worksheets to be updated manually.
For Each sld In ActivePresentation.Slides
For Each sh In sld.Shapes
If sh.Type = msoLinkedOLEObject Then
If sh.OLEFormat.ProgID = "Excel.Sheet" Then
sh.LinkFormat.AutoUpdate = ppUpdateOptionManual
End If
End If
Next
Next