จะ insert แบบมีการตรวจสอบก่อนจะบันทึก จะต้องใช้คำสั่งอะไรครับ

Dim connection As String = "Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True"
            Dim conn As New SqlConnection(connection)
            conn.Open()
            Dim comm As String = "INSERT INTO RENT(CH_IN,CH_OUT)"
            comm &= "VALUES(Convert(DateTime, '" & lblSeleceDate.Text & "', 103),"
            comm &= "Convert(DateTime, '" & lblSeleceDate1.Text & "', 103))"
            Dim command As New SqlCommand(comm, conn)
            Try
                command.ExecuteNonQuery()
            Catch ex As Exception
                Label1.Text = "ผิดพลาด"
            End Try
            conn.Close()