I have a report where you enter the start date and the end date.  I would like to have the person that runs the report be able skip the start and end date and get all records associated with that work center.  How would I do this in crystal 2008?

you could create 3rd string
 parameter type with 2 default values like
use date range
don't use date range

then in select expert
write something like
(if {type?} ="use date range" then
date_field in @start to @end
else 1=1)