i want to add a YES or No MsgBox to my Code

[HaroonSid]

Plz help
i have this code for Update Data Validation List Automatically......................i want to add a Yes Or No msgbox.......
code:

Private Sub Worksheet_Change(ByVal Target As Range)
Dim NewEntry As String
If Target.Cells.Count > 1 Then Exit Sub
If Target = "" Then Exit Sub

If Not Intersect(Target, Range("C61:C500")) Is Nothing Then
    NewEntry = ""
    NewEntry = Target
   If WorksheetFunction.CountIf(Sheet4.Range("NAME_SID"), NewEntry) = 0 Then
     Sheet4.Range("NAME_SID").End(xlDown).Offset(1, 0) = NewEntry
     Sheet4.Range("NAME_SID").Resize(Sheet4.Range("NAME_SID").Rows.Count + 0, 1).Name = "NAME_SID"
   End If
End If

End Sub