Off the top of my head I see three ways to do that. Depends on what exactly you're trying to achieve.
First you can source a view which delivers only the record in question.
Second you can set up a source filter for this particular table so that only the record in question is sourced.
Third you can build an Advanced Rule which checks whether the current record is the record in question and, if not, does nothing. But of course that means that the whole table will be sourced.
Again, it depends on the overall process, your question is a bit vague to me.