Create DateTime / LastUser Stamp

Hi,
 I would like to log all the changes in the database together with the Date/Time stamp and User Login.
Therefore, two additional fields are added modified_on, and modified_by, respectfuly...
FormView is used to edit each record and is bound to sqlDataSource using sqlDataSourceID...
of course, Form fields are bound as well...
How to assign values modified_on (date/time of the record update is inserted), and how to assign user login name to modified_by field?
(i would use User.Identity.Name.ToString(); to retreive user login name)

Thanks,
M.
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