Hi
try
Private Sub Worksheet_Change(ByVal Target As Range)
Dim counter
If Target.Cells.Count 1 Then Exit Sub
If Target.Column < 4 Then Exit Sub
On Error GoTo errhandler
Application.EnableEvents = False
With Target
If .Value = "" Then
.Offset(0, 1).ClearContents
Else
counter = Application.WorksheetFunction.Max(Me.Range("E:E")) + 1
.Offset(0, 1).NumberFormat = "0000000000000"
.Offset(0, 1).Value = counter
End If
End With

errhandler:
Application.EnableEvents = True
End Sub

--
Regards
Frank Kabel
Frankfurt, Germany


Pat wrote:
I want a unique number automatically inserted using the
Worksheet_Change event. When a cell in column D contains a value
column E will automatically display a unique 13 digit number which is
incremented by one. The worksheet will be sorted regularly, so taking
away the worry of knowing what the last number used to avoid
duplicates is vital.

Anyone got the know-how on this?
Many thanks!
Pat