Private Sub Worksheet_Change(ByVal Target As Range)
If Target.Address(0, 0) <> 'B1' Then Exit Sub
Range('b3').ClearContents
With Range('B3').Validation
.Delete
.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:= _
xlBetween, Formula1:='=' & Target
End With
End Sub