I used mail merge with SEQUENCE and KEY, as in your tutorial "Catalogue Mailmerge".
It worked like a charme, your tutorial is very good and useful.

I've found a way to write some text in the first page only, non repeated for every group, in this way:

{QUOTE{IF{MERGESEQ}= 1 "{SET Key ""} FIRST_PAGE_TEXT"}" ... }

Thanks for everything, my problem was solved!