I' m using crystal reports XI. I can easily create static parameters however I don't know how to create dynamic parameters with combo box?

I have a parameter field in number format. I have turned this field from static to dynamic from parameter fields. However each time when I refreshed the report data, same parameters came twice but I could not enter any value to the second time coming parameter box. Because I can not prompt any value in this field. Also this parameter box was not in the form of a combo box.

 

Should I enter all parameters manually or is there any selection making parameter' s selection available with a combo box?

 

Thanks.