[pmwiki-users] How to: calculate how many days left

[imoc]

I've been using PageList to set schedule reminders. It's as simple 
as this:

=============================
   Date       Appointment 
-----------------------------
2008-03-05  Lunch with Ellen
=============================

The 'Date' field is a PTV insert by hand. The 'Appointment' field 
is page title which I can click to edit or see the further detail.

Now I'd like to add a new field to show  how many days left from 
today to the due day. It will look like this:

=======================================
 DaysLeft   Date       Appointment 
---------------------------------------
    7     2008-03-05  Lunch with Ellen
=======================================

How to do this? Is this possible? Than for any help.

Cheers,
imoc