Function to read closed orders from history and calculate loss until first positive order

Function to read closed orders from history and calculate loss until first positive order.

For example (negative values in brackets),

1 order = 100, 2 = (100), 3 = (100). Total loss (200).

1 order = 50, 2 = (25), 3 = 25, 4 = (100), 5 = (50), 6 = (30). Total loss (180).

But.

I don't need to calculate loss for day etc. Just calculate backwards until first positive order and return result.