Customize and memorize crystal report fields

Question

Hi Techies,
    I am working on crystal report using C#.In that I want to create crystal report application such as to provide functionality to user -as User shud be able to select the fields to be displayed on report.
 e.g.Suppose we are displaying 5 fields on report as id,name,address,city,state.
    but user is interested in only 3 fields,later on if he wants to display 4 fields or in future he might be interested in more fields.
   So such sort of functionality i want to add to report while calling it.
        If any idea ..plz help me out..it urgent.
         Have  a nice time..

Best Regards,
Nilesh Jagdale