You can use Connexion's automatic stamp functionality to apply your holding code's value to the label.
1. In Connexion client, go to Tools > Options.
2. Under the Printing tab, select Label Options.
3. Click Define Automatic Stamps.
4. Enter the holding code value in the first field.
5. Choose to Assign automatic stamp to holding library code. Enter the value again in the field under this option.
6. Click Add. The holding code will appear under Automatic Stamps Defined.