[Orgmode] org-remember templates with dynamic target headline

[Daniel J. Sinder]

I want a remember template that will have a target headline based on the 
date on which I call org-remember.

For a simple example, the effect I'd like to achieve is shown by putting 
the following in my .emacs:

(setq org-remember-templates
      `(("Journal" ?j "* %u %?\n" "~/org/wjournal.org" 
,(format-time-string "%G: Week %V"))))

I'm an elisp noob, but I realize the problem here is that 
format-time-string is only evaluated once when my .emacs is read.  So, 
unless I restart emacs every week.  This doesn't work.

How can I cause format-time-string to be re-evaluated whenever 
org-remember is called?

Thanks,
Dan