title: Handling measurement units in NSTextField
body: <p>I am creating a test application to calculate the area of a rectangle.This application uses  <strong>NSTextField</strong> control to get the length and breadth of rectangle.<br>
  The user is expected to enter a string value which will include units of length as well (Sample Values <strong>2.5 inches</strong>, <strong>1500 mm</strong>).
  I want NSTextField to convert the value in centimeters (<strong>cm</strong>) automatically so that it displays the converted value (<strong>in cm</strong>) as soon as the text field looses focus. </p>
  
  <p><strong>For Eg:</strong></p>
  
  <p><strong>User Enters length as</strong>:  1500 mm</p>
  
  <p>As soon as user goes to next text field to enter breadth, the length field displays</p>
  
  <p><strong>Displayed Value</strong>:  150 cm</p>
  
  <p>How can we achieve this?</p>