Any time you then put in place the portfolio yet again by borrowing $S_ t_1 $ at charge $r$ you'll be able to realise a PnL at $t_2$ of $begingroup$ I estimate day-to-day pnl on the CDS placement using the spread improve times the CS01. Having said that I would https://www.youtube.com/watch?v=qMmsQ4kKgY4