[Quietseb]

The simplest way is to use a playlist.
The problem is, it won't allow you to define options. If you don't set options (such as default sub language etc), I think you should use a playlist.

If you absolutely want to use bsi files, you'll need to make one per movie file. you will have for example:

my_movie_part1.avi
my_movie_part1.bsi
my_movie_part2.avi
my_movie_part2.bsi

my_movie_part1.bsi will read:

[Main]
NumberCDs=2
CD=1
[Movie]
Title=Movie Title
Directory=.
FName=my_movie_part1.avi
FName2=my_movie_part2.avi

my_movie_part2.bsi will read:

[Main]
NumberCDs=2
CD=2
[Movie]
Title=Movie Title
Directory=.
FName=my_movie_part1.avi
FName2=my_movie_part2.avi

(note there is no FName1)

I tried with only one bsi file, it didn't work (as could be expected)
I also tried calling a playlist via the bsi file, which could have allowed to set options and play several files, but it didn't work either: only the first file is played