Setting gnus-message-archive-group in message-send-hook

[Marcin Wlodarczak]

Hi,

I'm trying to set gnus-message-archive-group depending on the From:
address, using the message-send-hook. Here is what I've got so
far:

(add-hook 'message-send-hook 'my-select-archive-group)
(defun my-select-archive-group ()
  (let ((from-address (mail-fetch-field "from")))
    (cond ((search "uni" from-address)
           (setq gnus-message-archive-group "nnimap+uni:Sent"))
          ((search "gmail" from-address)
           (setq gnus-message-archive-group "nnimap+gmail:[Google Mail]/Sent 
Mail")))))

The problem is, however, that this only sets the Gcc line for the
*following message* not the one being sent. What am I doing wrong
here?

Best,
Marcin