I don't understand exactly what you want to do. It seems you want to do something with the series index when a book is added to the library, specifically copying the maximum series index for a series to a custom column for all books in that series.
If I am right then you can do what you want using the
Action chains plugin. You would add the new book(s), ensure their series information is correct, select the new book(s), then use an action chain that uses a python action to determine the highest series index for a selected book then copy that number to your "Total series" column in all the other books in the series.
You could use an action chains event to set the series for new books but I think that would end in disaster. You can't guarantee for any given book that the next index is one higher then the last or even that the series is correct.
Ask in the
action chains thread for more help.