Logs to capture who accessed/changed Reports in Sql Sever Reporting manager

Hi,

I have one path in which 20 users will upload reports.The logs generated in IIS were having UserName(the user who accessed the reports or any one who changed the data) in them but When I am using WCF, logs are generated in a folder but the logs doesnot contain username who accessed the reports. I want to log the username who accessed the data. Can any one suggest me with a solution??

Thanks Attinder