setting .htaccess authentication with PHP

Hello Everyone, I've developed a feature which allows clients to upload files to a dir on the server. I want to allow clients to email a url to the file as follows :- http://www.mysite.com/clientX/file01.jpg I want to setup challenge / response authentication on the client folder so that when someone clicks the link they are prompted for a username / password. I'm thinking that apache .htaccess permissions are the best way to do this. The server is running Linux. My question is, can I write a PHP / shell script to automatically set folder access permissions and how would this be done? Thanks, Javier _________________________________________________________________ MSN Photos is the easiest way to share and print your photos: http://photos.msn.com/support/worldwide.aspx