Steps:
1. Create Main Report [Eg:myMainReport.rpt]
2. Create SubReport [Eg:mySubReport.rpt]
3. Pass parameters [From database/through code] to Main report
4. Choose which parameter(s) [Eg.{Discount}] you want to pass to Sub Report
5. Open mySubReport; Create a parameter in the format [Name]:{Pm-?ParameteName} [Eg:{Pm-?Discount}] as normal parameter field; Place this parameter in the app section of the report to display.
6. Open myMainReport; Select ‘mySubReport.rpt’; Right-Click, Click ‘Re-Import sub report’
7. Again Right-Click, Click ‘Change sub-report links’
8. In the new wizard choose ‘Available Fields’; then select ‘Discount’ under ‘Report Fields’; Drag this to ‘Field(s) to link to’ section
9. Under ‘?Discount field link’ dropdown list select {?Pm-?Discount}; This will gred-out ‘Select data in subreport based on field’ tick box and also its dropdown list,Finally click OK.
10. Done & Run to Check