It should be something like below <br><br> <code> function mymodule_civicrm_validateForm($formName, &$fields, &$files, &$form, &$errors) { if ('CRM_Event_Form_ManageEvent_EventInfo' == $formName) { if ( validation condition fails ) $errors['custom_element'] = ts('Validation message'); } } } </code> <br> HTH<br> Pradeep