I don't find that helpful - either I haven't explained myself well or there is something about styles I do not know - is there a way of creating a style that treats alternate lines differently, and if so how?

I'm aware how to define styles and apply them manually. What I have here are poems of many hundreds of lines - maybe over a thousand in some cases (e.g. Dante's divine comedy - over 400 pages) it's not hard to select each verse or canto and apply the first style - but then to go through, selecting every alternate line and apply the second style - that is the work of many, many hours. Surely it is the role of macros to automate the tedious and repetitive?