Access 2000 form/table design question

I have an Access table which keeps track of requests for information I get from my users. I am designing a form which will reference the user names, depts, etc. and put this into a drop-down box so that my assistant can select the relevant information from the list. Is there a way to remove duplicate names from the list in each field? Also, I want to be able to enter new data in each field via the form and have Access save that info so it will be there next time. How do I do this?