I am starting to write an org-capture template with a `file+function` tag.
It works pretty well if I put the function exactly with accordance to the
documentation[1].
However, I am trying to make this function to accept an argument to let it
find the store place programmably.
I did some investigation on the org source, but it seems that it is not
easy to work this out without hard code modification.

Can this be a new feature of org-capture? or you guys have an alternative
to implement this?

[1] http://orgmode.org/manual/Template-elements.html#Template-elements