Private Sub Worksheet_Change(ByVal Target As Range)
Dim Oldvalue As String, Newvalue As String
Application.EnableEvents = True
If Not Intersect(Target, Range("E6")) Is Nothing Then
Application.EnableEvents = False
If Range("E3").Value = "Yes" Then
Newvalue = Target.Value
Application.Undo
Oldvalue = Target.Value
If Oldvalue = "" Then
Target.Value = Newvalue
Else
If InStr(1, Oldvalue, Newvalue) = 0 Then
Target.Value = Oldvalue & ", " & Newvalue
Else:
Target.Value = Oldvalue
End If
End If
Else
Target.Value = vbNullString
End If
End If
Application.EnableEvents = True
End Sub