Silverlight upload with progress bar but trigger server side event passing filename

Question

OK, I'm quite new to c# and really, really new to Silverlight.  I've attempted to find the info I'm after by searching on the forums without success :(
 
Anyway, I'm trying to create a web-site where users can optionally login and upload a file(s) with a progress bar.  Sounds simple enough and I have found a few examples to do this but what I am having trouble with is finding a way to control the filename of the upload so that it is based on the user who is logged in (I'm actually using Profiles, so anonymous usernames are GUIDs)

In other words, I'd like a user to be able to upload a file to the server but I need to keep track of which user uploaded which file. 
Does anyone know of a Silverlight upload (with progress) that will upload a file to the server (say as a random GUID for a filename to an upload directory and then can trigger a server side event (passing the GUID filename) where I can access my profile/user information and record it in a database?  This is an example, of course, if anyone has any better ideas, all help is appreciated

This is my first post, so I'm unaware if there is any specific info you need, but I'll just say I'm using VS2008, ASP.NET 3.5 and Silverlight 3.
 
Thanks in advance

Phill
Edit: I thought i placed this topic in silverlight, but apparantly not, any chance a mod can move it please?  Thanks