Suppress Main Report header when subreport is detected

I have a crystal report that displays customer orders and shipping information for a range of customer orders. At the end of each customer order, a subreport runs that displays a required shipping form. Each page has header information about the customer order. I want to suppress this header information on the subreport pages. If I could detect when the subreport runs, then I could add a formula to the page header section to suppress when the subreport is detected. Thanks for your help.

Jeff