I would tag the text boxes I wanted to refit by putting something in the Alt Text property. This way you can use the same text every time
Code:
Sub ResizeTextInShapes()
Dim aShp As Shape
For Each aShp In ActiveDocument.Shapes
With aShp.TextFrame
If .HasText And aShp.AlternativeText <> "" Then
Do While .Overflowing
.TextRange.Font.Shrink
Loop
End If
End With
Next aShp
End Sub