Error message

• Notice: Undefined index: VestigePOS_TransferVoucher in drupal_retrieve_form() (line 763 of C:\wamp64\www\drupal-7.22\includes\form.inc).
• Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'VestigePOS_TransferVoucher' not found or invalid function name in drupal_retrieve_form() (line 798 of C:\wamp64\www\drupal-7.22\includes\form.inc).