[Dovecot] Last login fields

Hey guys, Wondering if anyone has tried to do this before - a last login timestamp field. Using mysql for auth, I figured it would be easy enough to add a timestamp field and then tack an UPDATE statement on the end of the password_query. But of course, dovecot sees this as only one statement to pass to MySQL - of which MySQL barfs at.. Any ideas on how to achieve this ?

Regards

Dean Manners