What distinguishes the "most current" survey data from the "oldest"?
If there is a date or serial number field that you can use, then Min ( RelatedTable::Field ) can return the date or serial number value of the oldest related record and Max ( relatedTable::Field ) can return the most recent. With a sorted relationship, you might also use the Last ( ) function to access data from the oldest or newest set of survey data. These expressions could be used in an unstored calculation field as an additional match field to match to just the records for the oldest or newest survey.
There are also scripts that could be used to find the oldest/newest ID or date to place in a global field that is used as match field.