[chaley]

You must use either general program mode (GPL) or template program mode. Which you choose depends on where the complexity is. In your case, determining in the template that there is more than one author might be a challenge, which would push me to GPL.

Here is a guess about what you might want expressed in GPL.

program:
	a=field('author');
	first_author =  sublist(a, 0, 1, '&');
	last_author=cmp(count(a, '&'), 1, '', '', strcat(' / ', sublist(a, -1, 0, '&')));
	authors = strcat(first_author, last_author);
	rest = template('{series:|| }{series_index:0>2s|[|] - }{title} ({pubdate:sublist(-1,0,\,)})');
	strcat(authors, ' - ',rest)