Sub UpdateDocumentHeaders()
Application.ScreenUpdating = False
Dim strFolder As String, strFile As String, wdDoc As Document
Dim strFnd As String, strRep As String, wdStory(), i As Long
strFolder = GetFolder
If strFolder = "" Then Exit Sub
strFnd = InputBox("Text to Replace", "Old String")
strFile = Dir(strFolder & "\*.doc", vbNormal)
strRep = InputBox("Replacement Text", "New String")
wdStory = Array(wdPrimaryHeaderStory, wdFirstPageHeaderStory, wdEvenPagesHeaderStory)
While strFile <> ""
  Set wdDoc = Documents.Open(FileName:=strFolder & "\" & strFile, AddToRecentFiles:=False, Visible:=False)
  With wdDoc
    On Error Resume Next
    For i = LBound(wdStory) To UBound(wdStory)
      MsgBox wdStory(i)
      With .StoryRanges(wdStory(i)).Find
        .ClearFormatting
        .Replacement.ClearFormatting
        .Text = strFnd
        .Replacement.Text = strRep
        .Forward = True
        .Wrap = wdFindContinue
        .Format = False
        .MatchCase = True
        .MatchWholeWord = True
        .MatchWildcards = False
        .MatchSoundsLike = False
        .MatchAllWordForms = False
        .Execute Replace:=wdReplaceAll
      End With
    Next
    On Error GoTo 0
    .Close SaveChanges:=True
  End With
  strFile = Dir()
Wend
Set wdDoc = Nothing
Application.ScreenUpdating = True
End Sub