I'm working on this worksheet and you folks have been wonderful in your
help.
Sometimes I accept your help without question but this time I need further
explanation..

Someone sent me this code which does the job but I think my next step
requires me to work with this same code and I only have a slight clue as to
what it means. If someone could explain what this code means in common terms
I would be greatly appreciative.

Private Sub Worksheet_Change(ByVal Target As Range)

   On Error GoTo ws_exit
   Application.EnableEvents = False

   With Target
       If Not Intersect(Target, Me.Range("A20:A23")) Is Nothing Then
           If .Offset(0, 1).Value <> "" Then
               If .Value > .Offset(0, 1).Value Then
                   MsgBox "Sorry, Invalid date!"
                   .Value = ""
                   .Offset(0, 2).Select
               End If
           End If
       ElseIf Not Intersect(Target, Me.Range("B20:B23")) Is Nothing Then
           If .Value <> "" Then
               If .Value <= .Offset(0, -1).Value Then
                   MsgBox "Date must be later then Start Date!"
                   .Value = ""
                   .Offset(0, 1).Select
               End If
           End If
       End If
   End With

ws_exit:
   Application.EnableEvents = True

End Sub

Thanks In Advance,

Barry

A copy of the worksheet can be downloaded from this address:
http://cjoint.com/?kut13HJGpY

My next step is to try and add code to evaluate  the contents of  cell B20 .
If B20 is greater than the 145th day of the year I would like to be able to
Set B20 to 145 and move the selected date to  B21 with A21= 145 and so
forth...