Crystal Reports - Parameters

I was wondering if someone can help me please, I've got a problem with parameters in Crystal Reports

The connection I am using is OLE DB (ADO) linking into a database in MS SQL Server. I have used the Add Command feature and created my own SQL query to retrieve the data from the database which works fine.

The problem I'm having is that the database table that I am trying to retrieve data from is quite large and is making the report take way too long to run. I have tried to get around this by adding a couple of Parameters in the Parameter List section in the Modify Command dialog box, these are prmDateBegin and prmDateEnd. This works fine, and manages to speed the report up significantly. The problem now is that I need to add another parameter which will produce the list of users that has been added to the database.

I have added another parameter in the report design time to dynamically bring back the list of users from the database, but now when the report is run the users gets prompted for the date parameter twice! Does anyone know of a way to ensure that the users will only get prompted once for the parameters?

Please can anyone help me!! :(
Thanks