Lets go back the hte beginning and take care of the duplicates problem. This code is from your first post. IF it worked before, it should work now with no duplicates. After this is proven, then, if you want, we can incorporate snb's method of file handling from the above mentioned thread.

Function ListFiles(ByVal FolderPath As Variant, Optional ByVal SubfolderDepth As Long)
     
     ' Subfolder depth: -1 = All subfolders, 0 = No subfolders, 1 or any positive value = maximum depth
     
    Dim dot         As Long
    Dim ext         As String
    Dim n           As Long
    Dim NewName     As String
    Dim oFile       As Object
    Dim oFiles      As Object
    Dim oFolder     As Variant
    Dim oShell      As Object
    Dim Wkb         As Workbook
    Dim NewBook As Workbook '<<<<<<<<<<<<<<<<<<<<<
    Dim WkbName     As String
    Dim Wks         As Worksheet
     
    If oShell Is Nothing Then Set oShell = CreateObject("Shell.Application")
     
    If FileFilter = "" Then FileFilter = "*.*"
     
    Set oFolder = oShell.Namespace(FolderPath)
    If oFolder Is Nothing Then
        MsgBox "The Folder '" & FolderPath & "' Does Not Exist.", vbCritical
        SearchSubFolders = False
        Exit Function
    End If
     
    Set oFiles = oFolder.Items
     
     ' Return all the files matching the filter.
    oFiles.Filter 64, FileFilter
     
     'Split each workbook's worksheets into new workbooks.
    For n = 0 To oFiles.Count - 1
        WkbName = oFolder.Self.Path & "\" & oFiles.Item(0).Name
        Set Wkb = Workbooks.Open(WkbName, False, True)
        dot = InStrRev(Wkb.Name, ".")
        ext = Right(Wkb.Name, Len(Wkb.Name) - dot + 1)
        WkbName = Wkb.Path & "\" & Left(Wkb.Name, dot - 1)
        For Each Wks In Wkb.Worksheets
            NewName = WkbName & "_" & Wks.Name '<-<-<-<-
            Wks.Copy
            'Immediately set a variable the newly created book
            Set NewBook = Workbooks(Workbooks.Count) '<<<<<<<<<<<<<<<<<
            NewBook.SaveAs NewName & "_" & Left(CStr(CDbl(Now)), 10) & ext '<<<<<<<<<<<<<<
            NewBook.Close '<<<<<<<<<<<<<
        Next Wks
        Wkb.Close SaveChanges:=False
    Next n
     
     ' Return subfolders in this folder.
    oFiles.Filter 32, "*"
    If oFiles.Count = 0 Then Exit Function
     
    If SubfolderDepth <> 0 Then
        For Each oFolder In oFiles
            Call ListFiles(oFolder, SubfolderDepth - 1)
        Next oFolder
    End If
     
End Function