Custom Crystal Report Criteria

I am trying to build a crystal report that will display select information from my database in a format that is standard to all of my users. My problem is that I would like the information that displays in the report to be customized depending on which user is requesting the report. Assuming that my web app successfully logs in a user and authenticates who they are and stores the necessary key data into global variables (employee number, unit number etc.), how do I change the data that displays in the report at runtime based on these criteria?

Can a query be generated at runtime based on the login that is used for the report? Can this be done with a dataset? I have been working with the WROX book Professional Crystal Reports for Visual Studio .NET but have been unsuccessful in all attempts to get this working. Any tips that may point me in the right direction are greatly appreciated.