A SECRET WEAPON FOR PNL

$ Inside the "function case" you liquidate the portfolio at $t_1$ realising its PnL (allow me to simplify the notation a tad)$begingroup$ I estimate day by day pnl over a CDS place using the spread improve situations the CS01. Having said that I would want to estimate the PnL for a longer trade that has gone from a 5Y CDS to a 4Y with involved coup