This is version dependent.
If you think about Alex's solution, the application is passing SQL, the SQL is doing the update.
Version 9 allows for passing SQL, but more importantly, you can create a Stored Procedure to perform whatever updates you need.
I would take Crystal out of the picture entirely though.
If you insist on using a presentation program to update data, consider that you could read data in a Main report (remember this is version 9), pass it to a subreport, update from the subreport SQL, just make sure that you issue a select after the update so that Crystal gets a data set.
-k