[horde] Add new term to sort

[Mike Poznecki]

Hi, I need to add a new term to the sort.  I have already added the new column and the data is showing up correctly.  But when I click on the header to sort, Horde throws and error.
I've been trying to trace the code.  So far, I started in ListMessages.php which somehow calls Imap.php which does a call_user_func_array($this->ob, $method).
But I do not know where it goes from there.  Can anyone help me figure out where to go look so that I can get it to use the new term?
Thanks.