I run a website ([login to view URL]) which uses Drupal and CiviCRM. CiviCRM maintains details of contacts and we have added some custom fields which are displayed against each contact. One of those fields contains an ID of contacts in third party website. The software we use provides for any custom field to contain php code. We wish to construct a clickable URL inside a custom field which is made up of a literal and the contents of another custom field.