There are a number of methods you can use depending on the structure of your data, the current state of your database and what exactly you need to do with this value.
getNthRecord (fieldName ; Recordnumber ) refers to records in the current found set. Thus performing a find, changing layouts and/or sorting the records can all affect what value is returned.
getNthRecord ( RelatedTable::FieldName ; Recordnumber ) refers to the records in "relatedTable" that are linked to the current record. Changing records or layouts can both affect what record is referenced.
You can also define relationships that match to a specific record in the same table or another table.
Scripts that search and/or sort records can be used to refer to data in another record.
In some cases, calculation fields and filtered portals can be used to refer to data in a different record or group of records.