trying to keep private info private (1 Viewer)

I am working on an ADP project (using SQL Server Express) that will contain personal info and work/project info on employees. I need to set up the forms (or tables?) so that each employee can only access his/her own personal info and so that they can only EDIT/UPDATE thier own project info but can VIEW projects of others. I am finding all kinds of good stuff about the Windows Integrated Security that I have the system set on only allowing someone in the allowed group to open the database, but how can I limit access in the way described above - once they are in the database? Does the WIS pass the users' password or something like that into the database that I could use in a lookup table - or ?????

Thanks for any help!!!!