No, it is not possible.
1) The virus definition files for Avast 32 3.0 and avast! 4.0 aren´t compatible.
2) There´s no way to setup avast! 4 on workstations to look for for updates on any other server than our own (ASW servers).
The features you are looking for will be available in avast! 4 NETWORK edition - we plan to release this edition this summer, so be patient, please.