.htaccess mod rewrite automatically using php or something?

[godman]

I've got a number of users, each with the website page like http://www.mysite.com/folder/artist_id.php?id=33The users need to be able to set their own easy URL such as http://www.mysite.com/userguy that would redirect to the above page.I know how to write these out manually in .htaccess with RewriteRule but, for example, users have a whole control panel created with php and javascript and it's become necessary to allow them to choose the name themselves and have code automatically put in. But I don't have a clue if there's already an easy method of setting that up or adding to the .htaccess file via code or if I should just do some sort of file open, rewrite thing, or what's safe. BTW, I'm not worried about issues such as them naming themselves the same as an existing folder or php file in my site. The users are limited and subject to approval so that shouldn't be a problem.