Wordpress - using authors first, last, name in url for a list of posts

I would like to have links on my site that will go to a page that displays all of a users posts.

I have not used it in the past, but it looks like wordpress does it easily enough, apparently using the 'archive.php' page in my theme.

So I can have a url like this:  www.mysite.com/author/username  and it will display their posts very nicely.

Here's the problem I am dealing with though... in the past, some of my users choose different usernames than the names they write under. When writing, we list their first & last name as the 'author'.

So if I go with the way things are set up write now - the url might be www.mysite.com/author/andy  (the username being the author's real first name)  when the "author's name" on the post is Jacob Long. It makes it look a bit goofy.

Is there a way I can set wordpress up to use a url like this: www.mysite.com/author/firstName-lastname  to list the posts from that author?

Setting up the links is easy enough using:

$user->user_firstname . '-' . $user->user_lastname

in the url. But of course, that link does not work unless they happened to use their full name as their user name.

I'm not even sure if I would tackle this issue in the .htaccess, index.php, header.php, archive.php, or some wordpress file?

Thanks for any help on this,

Chris