ObjectDataSource -Parameter Source Session

[Alejo]

hi.
I am currently using "form" authentication ( asp.net's membership and role
management) in my app, I wanna use the objectdatasource control to fill data
into my gridview but I need give a parameter to get the data. This parameter
is the UserId wish is inside the session in my app.
I don't know how item select in the "Parameter Source" combo box in the
objectdatasource, in order to get the UserId of my session and what write in
the "Default Value" text box

Thanks for the answers.