Well, .ass files don't work well due to the frequency by which they get wiped after emitting processed data. You should try .cok or .psy files instead.
I forgot to add: There is a technique for embedding a .cok file in an .ass file for greater utility, but the result often triggers the system's virus checker. It's just not worth doing.
"The first part, packass.exe, creates an .ASS file from multiple source files. The other part, assio.c, is linked with your application to support reading from the .ASS file."