Custom User Paths for Uploads

This is for ASP.net with VB.net

I'm trying to configure it to upload/browse to paths depending on the user thats logged in.
After login (before the page with the control on) I set

Session("FCKeditor:UserFilesPath") = "~/UserFiles/" & Session("username")

But for some reason it always saves and browses to the userfiles folder.

All help appreciated, many thanks.

Dann