title: Drupal custom field which open a popup
body: <p>I'd like to create a custom field in Drupal 7. This field should have a textfield and a button, when the user click on the button, it open a popup which load an external page, this page generate a link. Then the user copy and past this link in the textfield.<br/>
  My question is, how can I create this custom field which open a popup window ?</p>
  
  <p>Any suggestions?</p>