Depends on how the report is getting data. If it is calling a stored proc, you would need to pass the record displayed on your form to the proc and have it filter the data. If you are pushing the dataset to the report, you could use linq or a loop to filter the dataset to only have the data for the record that is displayed.

For pushing the data, you can have the app call the stored proc, then filter out the records that are not needed and finally set the reports.DataSource to the filtered dataset (or it can be a datatable).

HTH