how to restrict drill down to sub-report in crystal reports

Hi

I am having drill down issue will Crystal Reports for Enterprise. When a report with sub-report is published to the enterprise server and if a user moves the mouse pointer on to the sub-report and click, it is drilling down to the sub-report. I need to restrict this behaviour.

I tried placing a text box on sub-report and had no luck.

Any help is appreciated.

Thank you,

Sri