I don't know of any way to achieve this, but imagine that it would involve heavy customisation of the inbuilt sme events, and as the passwords are securely stored would not only prove to be a difficult task but probably not advised.
Perhaps you can achieve what you want through a different method - for example you maybe able to authenticate against the existing smeserver database. If your query to the forum gave more of an indication of why you need the passwords in a separate database you may get more responses outlining viable alternatives.
Just a suggestion, as I note your request has not been replied to yet.
Cheers, Shell