Hi,
You mean user selects RC1 and RC3 and data related to those 2 RC's only needs to be displayed?
If yes, try creating a multi value parameter in Crystal and have a default value (say All).
using record selection, you can check for the values selected by users like:
if {?parameter} = 'All' then true else
<database field> in {?parameter}
Replace {?parameter} and <database field> with your parameter and database fields respectively.
Let me know if this your requirement.
Thanks,
Raghavendra