help me configure WP All Import plugin to update woo commerce product stock

I use wp-all-import plugin to update woo product stock via a CSV file The CSV file contains a date field, of last modified stock date. (otherwise the process becomes very slow, if we need to go through all products every time) The CSV also contains the stock update through 3 columns, but I need a very simple formula (X + Y - Z) in order to get the actual stock. I believe that all of this can be done through WP-All-Import (updating x-path for filtering and using the php function when processing the stock field) but if not it can be done through a php script outside. Should be a very simple task with few lines of code. If you are up for it? let me know. Thanks