Sub report linking problem

Hi All,
I am working in Crystal Reports XI. When I add an on demand sub-report to the main report the hyperlink disappears when I link the two reports. I am just trying to share the date from the main report to the sub-report. The main report runs a stored procedure that creates tables divided up by location. I want to be able to click on the location in my main report and have it open the corresponding sub-report. I created a beg_date and an end_date parameter and then put each of those into a formula to pass to the sub_report. The linking works to the degree that the dates are correct in the sub-report and the data falls within said dates, BUT the link in the main report turns invisible. I have scoured the net to find that others have come across this same problem, but have yet to find an answer on how to fix it. Does anyone know how to correct this so I can fix my report and restore a small part of my sanity? Your help is greatly appreciated. Please let me know if you need anymore information.

Thanks