Sub AttachNewTemplate()
Application.ScreenUpdating = False
Dim strFolder As String, strTmplt As String, strFile As String, wdDoc As Document
With Application.FileDialog(msoFileDialogFilePicker)
  .Filters.Clear
  .AllowMultiSelect = False
  .Filters.Add "All Word Templates", "*.dot; *.dotx; *.dotm", 1
  If .Show = -1 Then
    strTmplt = .SelectedItems(1)
  Else
    Exit Sub
  End If
End With
strFolder = GetFolder
If strFolder = "" Then Exit Sub
strFile = Dir(strFolder & "\*.doc", vbNormal)
' Create a temporary Word session to do the processing
Dim wdTmp As New Word.Application
wdTmp.Visible = False
'wdTmp.DisplayAlerts = wdAlertsNone
While strFile <> ""
  Set wdDoc = wdTmp.Documents.Open(FileName:=strFolder & "\" & strFile, AddToRecentFiles:=False, Visible:=False)
  wdDoc.AttachedTemplate = strTmplt
  wdDoc.Close SaveChanges:=True
  strFile = Dir()
Wend
Set wdDoc = Nothing: Set wdTmp = 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