It is not possible to deduce what is wrong from your description. Can you supply more details, do you use any interface inheritance in your call back interface, for instance? Sai-Lai -- E-mail: S.Lo@orl.co.uk | Olivetti & Oracle Research Lab | 24a Trumpington Street Tel: +44 223 343000 | Cambridge CB2 1QA Fax: +44 223 313542 | ENGLAND