Hilfy is the resident Crystal Enterprise expert on the forum and she has already done similar things. Search the forum for her posts and you'll find something similar that I remember being posted months back. Here is some generic info that might help.

Yes, you can pass a parameter to a stored procedure. Simply create the stored procedure with the necessary Input parameter and then create a new report using that stored procedure as the data source. CR will create a parameter in the report that will pass the data to it. The problem is that you need to populate the parameter with the user name prior to running the report. Otherwise, the user will be prompted to enter their user name prior to running the report (this might be ok, but most likely an irritant to the user). If you are using CR.NET, then you can do this programatically using the object model. Most likely, you are just using plain CR XI. Another option is to make the report a subreport of a blank main report. In the main report, use a formula to get the user name and then link that formula to the subreport's user name parameter. When the subreport runs, the parameter will have the correct user name in it and pass this to the SP.