File read and sort question

I have a directory with an ever-changing number of files. Some will be removed and others added on a continuing basis. The files are ascii with the following layout: <SENDER> Name <SUBJECT> Subject line <RELEASE_DATE> mm/dd/yyyy <RELEASE_TIME> hh:mm I can easily get a list of files and pull the necessary information. I need, however to be able to sort by RELEASE_DATE *and* RELEASE_TIME Philosophically, what is the best way to handle this? I'm hesitant to pull all the information into an array and use ksort since there are, on average, ~1000 messages in this directory which need to be processed. Susan