"Parameter source" for membersihp"s UserId?

Hi,

I have a ObjectDataSource bound to a GridView. The ODS uses BLL object
that expects UserId of the currently logged in user (Guid type) for its
select method. Is there a way I can declaratively pass the UserId to the
BLL? Neither of the parameter sources found in the Configure Data Source
seem to fit. Is there a way to do that or do I need to do it
programmatically?
I'd appreciate _any_ suggestions.

Thanks,
Bogdan