Private Sub Worksheet_Change(ByVal Target As Range)
    If Target.Count > 1 Then Exit Sub
    Application.EnableEvents = 0
    r1_ = Range("C" & Rows.Count).End(xlUp).Row
    If Not Intersect(Target, Range("C5:C" & r1_)) Is Nothing Then
        If Target = 1 Then
            m_ = WorksheetFunction.Max(Range("D5:D" & r1_))
            If m_ < Range("A5") Then
                Target.Offset(, 1) = m_ + 1
            Else
                Target = 0
            End If
        Else
            If Target.Offset(, 1) Then
                Target.Offset(, 1) = 0
                For i = 5 To r1_
                    If Range("D" & i) > Target.Offset(, 1) Then
                        Range("D" & i) = Range("D" & i) - 1
                    End If
                Next i
            End If
        End If
    ElseIf Target.Address(0, 0) = "A5" Then
        For i = 5 To r1_
            If Range("D" & i) > Target Then
                Range("C" & i).Resize(, 2) = 0
            End If
        Next i
    End If
    Application.EnableEvents = 1
End Sub