VB.NET โค้ด AUTORUN ID อยากใส่ปีกำกับ ปี ให้ ทำอย่างไรดีครับ

Sub autoid()
        Dim Today As Date
        Today = Date.Now
        Try
            Dim drTmp As OleDbDataReader
            Dim sqlTmp As String
            sqlTmp = "SELECT cost_id from Cost order by cost_id DESC"
            connect()
            With da
                .SelectCommand = New OleDbCommand(sqlTmp, conn)
                .Fill(ds, "cost_id")
            End With
            Dim sql As New OleDbCommand
            With sql
                .CommandType = CommandType.Text
                .CommandText = sqlTmp
                .Connection = conn
                drTmp = .ExecuteReader
            End With
            
            If drTmp.HasRows Then
                drTmp.Read()
                Dim i As Integer = 0
                Dim strTmp As String
                strTmp = drTmp(0)
                i = strTmp.Substring(1)
                i += 1
                txtcost_id.Text = "C" & i.ToString("00000")
            Else
                txtcost_id.Text = "C" & "00001"
            End If
        Catch ex As Exception
            MessageBox.Show("เกิดข้อผิดพลาด เนื่องจาก " & ex.Message, "ผลการตรวจสอบ", MessageBoxButtons.OK, MessageBoxIcon.Information) 'โชว์ messagebox เเจ้งผู้ใช้
            conn.Close()
        End Try
    End Sub