are these the tables in the database or the databases?
If you want to use multiple databases, not tables, the only solution that comes to mind is a stored procedure, which will need to be in the database that the connection is pointing to. In the stored proc, you can have the code select from the correct database. Crystal can only 'see' 1 database at a time.
Also, unless this is being called from an app, you don't pass things to the report, the report selects based on inputs made to the report. If you are going to pass anything to the database (you are using an app) why not have the app collect the data and pass that to the report?
HTH