Macro to save duplicate file and create folder name based on cell value

I currently use the following code to create a duplicate file based on two cells within a directory and folder i specify. These cells consist of the team and week commencing date (mondays date of week which is cell 'Main Menu'!K8)

Private Sub Workbook_BeforeSave(ByVal _
  SaveAsUI As Boolean, Cancel As Boolean)
    With ThisWorkbook
        .SaveCopyAs ("\\dfz70588\106124001\workgroup\Fraud Error Strategy Team\Recovery\Roll up work\testfolder\" & Range("'Main Menu'!H5").Value & ("-") & Format(Range("'Main Menu'!K8"), "DD.MM.YYYY") & ".xls")
    End With
End Sub

However I now want to be able to create an archive of past weeks duplicates by creating a folder based on the week commencing date ('Main Menu'!K8). I want the above macro to first check if the folder exists and if not to create it with the date ('Main Menu'!K8), if it does to simply save itself to that folder.

Thanks for any help