vsftpd - chown on upload

Hi

Recently I installed vsftpd on my linux machine (redhat 9.0). The server
works fine, but I have some configuration problems:

I've several user-accounts for uploading (NOT anonymous). If they upload
some files, it should be impossible to download them again. Only one
administrator account must can download and delete these files.

With wuftpd (which was installed on my previous server), I made a user and
permission change (in ftpaccess):

So "user1" has uploaded a file. Now ownership and permissions are changed to
user "admin", chmod 600.

With vsftpd I can change the permissions (local_umask), but NOT the owner.

Is it possible to change the file owner on file-upload? Have somebody
another idea to solve this problem?

Thanks in advance.

Greetings
Juerg