I have the same question. My guess is you don't have control of this and that you would have to create code that uses a windows form and a report viewer control. You can then use dropdown controls and such to present your parameters. Hopefully there's a trick that can be done that doesn't require a custom program. Anyone?
I have a similar request at the below thread: is there a better way to allow users to choose from a list of items when there are many items in a dropdown list? Scrolling a long dropdown list is very tedious.
http://www.sqlservercentral.com/forums/shwmessage.aspx?forumid=150&messageid=317890