Hi
It depends on how you define "the session".
I have added a condition to the trigger which will only update the current loss if the total won/lost amount is less than zero
"the session" is set using this setting:
Settings > General Options > Account Statement > Retrieve data not older than 0 days
this means win/lose variables will be valid only for the current day
In summary, the amended trigger will only start to work and recover a loss if the overall win/lose value for the day is negative. But you must make the settings change as mentioned above.
Please try it in test mode.