Starting with a new presentation and making it from scratch so shape
names will match up. We can modify this as we go along.
***Start Code***
Public Sub sldPrep()
'Make text box, fill with text, establish font size
With ActivePresentation.Slides(1).Shapes
   With .AddTextbox(msoTextOrientationHorizontal, 0, 252, 568, 36.85)
       .Name = "Text Box 4"
       With .TextFrame
           .TextRange = "       Now is the time for all good men to
come to the aid"
            With .TextRange.Font
               .Size = 23
            End With
       End With
   End With
'Make magnifying lens, remove fill
   With .AddShape(msoShapeOval, 0, 444, 96, 96)
       .Name = "Oval 5"
       .Fill.Visible = msoFalse
   End With
End With
***End Code***
Once the above shapes have been drawn on the slide, make an action
setting for the magnifying lens shape. Have it run the "MagnifyText"
macro. In slide show mode, the effect will take place when the lens is
clicked. Some adjustments will to be made. Post back when you get to
that point.

***Start Code***
Public Sub MagnifyText()
Dim i As Integer
With ActivePresentation.Slides(1).Shapes("Oval 5")
   .Top = 222
   .Left = -36
End With
For i = 0 To 90
With ActivePresentation.Slides(1).Shapes("Oval 5")
   .Left = .Left + 10
   With ActivePresentation.Slides(1).Shapes("Text Box 4").TextFrame
       .VerticalAnchor = msoAnchorBottom
       With .TextRange
           .Characters(i, 5).Font.Size = 44
           .Characters(i - 5, 5).Font.Size = 23
       End With
   End With
End With
SlideShowWindows(1).View.GotoSlide 1
Next i
With ActivePresentation.Slides(1).Shapes("Oval 5")
   .Left = 0
   .Top = 444
End With
End Sub
***End Code***