Why do you need to use a subreport? If I were doing this and using tables in the report, I would create several SQL Expressions that would split the long field data. If I were using a command to provide the data for the report, I would do the splitting as part of the query in the command.
The problem with using subreports is that they create a separate connection to the database and run a separate query EVERY TIME they run. So, if you have run subreport that is located in the details section, it will connect to the database and run a query for EACH detail record in your main report. There will be times when you have to use a subreport to get the data you need, this is not one of them.
-Dell