You can't use a find or constrain found set for this from the context of a summary report.
There is a scripted method that works or you can come at this from a different direction that does support performing a find.
You can use Sort Records to group your records for a summary report, and then you can re-order the sorted groups using the value of one of your summary fields--such as the one that counts attendance. A looping script could then loop through your records and omit groups of records for each person whose attendance subtotal does not meed the desired criteria.
Two tricky parts:
- Use GetSummary to get the value of your summary field so that you get the subtotal and not the grand total.
- In your script, you will need to check the value of this subtotal first and if it doesn't match the specified attendance level, then omit all records for that person. If you check the subtotal after each omit, the attendance will appear to drop by one each time so only check once before omitting all records for a given person.
To come at this from a different direction, if you could pull up a report with one record for each parishoner with a calculation field that counts attendance, you can perform a find specifying criteria for that unstored calculation field.