I haven't done anything dynamically in Crystal, as it doesn't seem to like it. I realize in theory, that it is all dynamic, but it seems from listening to others and the problems that they have run into, that Crystal is not a big fan of this.
The steps that would need to be taken,
create subreport
add subreport to main report
set links from main report fields to subreport parameters
set subreport datasource
All would need to be done in code, don't have any hints on that as a) haven't done it myself, b) work in a .Net shop.
Good luck, have fun