Your question has been up for less than half an hour, people are less inclined to help if you keep bleating on.
If your dates are in column A, then try this code inserted into a module in the VBA editor: -
Public Sub SavebyHighestDate()
Dim rng As Range
Dim myDate As String
Dim myPath As String
myPath = "C:My Documents"
Set rng = Sheet1.Range("A:A")
myDate = Format(WorksheetFunction.Max(rng), "dd-mm-yy")
MsgBox Format(myDate, "dd-mm-yy")
ThisWorkbook.SaveAs myPath & myDate
End Sub
Change the path, sheet no and column range to suit.