Sub UpdateDocumentHeaders()
Application.ScreenUpdating = False
Dim strFolder As String, strFile As String
Dim wdDocTgt As Document, wdDocSrc As Document
Dim wdRngSrc As Range, wdRngTgt As Range
Dim Sctn As Section, HdFt As HeaderFooter
strFolder = GetFolder
If strFolder = "" Then Exit Sub
Set wdDocSrc = ActiveDocument
strFile = Dir(strFolder & "\*.doc", vbNormal)
While strFile <> ""
    If strFolder & "\" & strFile <> wdDocSrc.FullName Then
        Set wdDocTgt = Documents.Open(FileName:=strFolder & "\" & strFile, _
        AddToRecentFiles:=False, Visible:=False)
        With wdDocTgt
            For Each Sctn In .Sections
                'For Headers
                For Each HdFt In Sctn.Headers
                    With HdFt
                        If .Exists Then
                            If Sctn.Index = 1 Then
                                Set wdRngTgt = .Range.Characters.First
                                wdRngTgt.End = wdRngTgt.End + 51
                                Set wdRngSrc = wdDocSrc.Sections.First.Headers(HdFt.Index).Range.Characters.First
                                wdRngSrc.End = wdRngSrc.End + 51
                                wdRngTgt.FormattedText = wdRngSrc.FormattedText
                            ElseIf .LinkToPrevious = False Then
                                Set wdRngTgt = .Range.Characters.First
                                wdRngTgt.End = wdRngTgt.End + 51
                                Set wdRngSrc = wdDocSrc.Sections.First.Headers(HdFt.Index).Range.Characters.First
                                wdRngSrc.End = wdRngSrc.End + 51
                                wdRngTgt.FormattedText = wdRngSrc.FormattedText
                            End If
                        End If
                    End With
                Next
            Next
            .Close SaveChanges:=True
        End With
    End If
    strFile = Dir()
Wend
Set wdDocSrc = Nothing: Set wdDocTgt = Nothing
Application.ScreenUpdating = True
End Sub

Function GetFolder() As String
Dim oFolder As Object
GetFolder = ""
Set oFolder = CreateObject("Shell.Application").BrowseForFolder(0, "Choose a folder", 0)
If (Not oFolder Is Nothing) Then GetFolder = oFolder.Items.Item.Path
Set oFolder = Nothing
End Function