Days between dates

Days between dates

Hi,
 
From a previous question on the forum regarding the number of days between dates the following code was provided.
  1. var first = '21/04/2009';
  2. var second = '25/04/2009';
  3. var days = parseInt(second.substring(0,2)) - parseInt(first.substring(0,2));
I have text boxes for "from", "to" and "days". I need help to show how I use the above to display the days.
 
Joe