What version of FileMaker are you using? I think your best bet is to filter the portal--which can be done for any version, but the details vary for FileMaker 11.
It is FileMaker Pro 8
I don't have that version so the exact details to set this up may be a little different from my version, but here's what I am suggesting you do:
Define a date field, SelectedDate, in the person table. This can be a global field if you want it to be.
Create a new relationship to use with your portal like this:
Person::PersonID = Surveys::PersonID AND
Person::SelectedDate = Surveys::CreationDate
If you also need a relationship that soley matches by PersonID, you'll need to create a second table occurrence of Surveys so that you can set up two different relationships to surveys.
You can now enter or select a date in the SelectedDate field and the portal will only show the survey records for the current person that have that creation date.
If FileMaker 8 allows you to use inequality operators such as < and > in your relationships, you can set up two dates and a relationship that then allows your portal to display a range of records.