Identifing Files

Main objective is that I need to identify all mp3 files played in my player. I am building my own music player. When I add a file from a directory to plist , I need to identify it. If it has played before , player count. I need to do something like writing - editing file metadata information. First , Is there any GUID information in file metadata informations ?

And if not , How can I write a guid information to file if does not exists and if exists I want to read play count. I want something belongs to me that I want other player like iTunes to write on my datas