Warner,
What i exactly told my first post....You can proceed this way .
First main report process then after the subreport checking all required links from main and executes based on section. you can put the subreport in report header then this executes. CR follows a top-to-bottom, left-to-right processing approach.
Pass a parameter from main to subreport like this follows:
Right-click the sub-report and select 'Change Sub-report links' -> ok
Subreports will (most of the times) slow the report
Thanks,
DJ