Private Sub Worksheet_Change(ByVal Target As Range)
Dim Changed As Range, c As Range
Dim s As String
Set Changed = Intersect(Target, Columns("A"), Rows("2:" & Rows.Count))
If Not Changed Is Nothing Then
Application.ScreenUpdating = False
Application.EnableEvents = False
For Each c In Changed
s = c.Value
If Len(s) > 1 Then
If Mid(s, 3, 1) <> "/" Then
c.Value = Replace(s, Left(s, 2), Left(s, 2) & "/", 1, 1)
End If
End If
Next c
Application.EnableEvents = True
Application.ScreenUpdating = True
End If
End Sub