You will need that Sub to keep a list of files already extracted and add a function to it that ignores any file already listed
One method is:
Declare Module level Constant
Const ListCol As String = "L" 'Edit to suit your needs
Add to Sub ExtracData before FileName = Dir
Columns (ListCol).Cells(1) = ThisWorkbook.Name
Change:
If fileName <> ThisWorkbook.Name Then
To
If Not Listed(FileName) Then
Cells(Rows.Count, ListCol).End(xlUp).Offset(1) = FileName
Add New Function
Private Function Listed(FileName As String) As Boolean
Dim List As Variant
Dim i as Long
List = Cells(1, ListCol).CurrentRegion.Value 'CurrentRegion require List of File Names be surrounded by empty cells
For i = 1 to Ubound(List)
If List(i) = FileName Then
Listed = True
Exit Function
End If
Next i
End Function