Problem with "Select Expert" in Crystal Report [Resolved]

I knew that we can customize the report (display a particular of entry) in Crystal Report by using "Select Expert". But this is when in during design time.

What if I want to set the "Select Expert" formula during run time?
Eg: there may be a list of options... like:
display all name start be A or B or... or Z
display all name who live in USA...

How can I do so?

Please guide. Thank you.

Either define a formula field and base your selection on that formula, then you can use that field in your code. Also you can define a parameter filed and base selection on that. If you use parameter then you will be prompted for value each time the report is loaded or refreshed.