You would have to set the file up as a data source for the report.  The problem with this comes if you're using the data from the text file to filter the data in the report.  If this is the case, the report will NOT push the selection criteria down to the database.  Instead, it will load all of the data into memory and filter the data in memory instead of pushing the selection criteria down to the database to filter the data there and only return the records that the report wants.  If the data that the report would pull without any selection criteria contains a lot of rows, this means that the report would be significantly slower than if you just use a parameter - first, because there's a lot more data that will have to be pulled in from the database and second, because Crystal is not as efficient at filtering data as a database is.  This could also take up a significant amount of disk space as Crystal does a lot of swapping data to and from a temp file while it's processing it under these circumstances.  I would test it both ways to determine the impact before just letting the user have what he wants - especially if there's not a really good reason for it other than a user want.