I am making a Timesheets program for my company. The company works on different projects and Each employee will book time to different jobs/Projects, that he/she worked on during a particular week. I am basically making the Timesheet program as an extensions to an existing database system. It has two tables Proposal and Projects. Now employees may book time to either a proposal or a Project. This seems to be an optional relationship case i.e. a timesheet record may have a project entry or a proposal entry. The Employee should be given a chance to select either the Proposal No or the Project No for which he wishes to book time to in the timesheet application. Now my questions is how do I implement this optional relationship in MS Access? It's easy to do it on an relationship diagram, but how do I actually implement it a physical level? I would really appreciate some suggestions from all you Access Masters out there. Thanks for all your time and efforts, in advance.