For those who did not find the solution:
http://help.zennolab.com/en/v5/zennoposter/5.1/ZennoLab.Macros~ZennoLab.Macros.FileSystem~FileGetLines(String,String,Boolean,Boolean).html
As numberOfLine you can pass ranges as described in wiki article.
http://wiki.zennolab.com/doku.php?id=en:ranges