Changing DB Driver using RAS

I have a reporting tool that runs reports that have been designed in either MS Access or Oracle environments. I basically need to know how to set the report's DB driver at run-time. I can set up the log in information specifying which DB to actually point to, but I am having a "logon failed" issue when trying to run a report that was designed with a different driver than the target DB type.

I'm using Crystal 2008 in Visual Studio .NET 2003.

Thanks,

Chuck