Hi,
Firstly, you'd need a table which defines who is allowed access OR the password used to log in.
Create a form with an unbound text box which looks up the user field in your table. You can then have the database open a default form for everyone or a specific form for each individual user.
Another way is to have the form's unbound text box open with a default value of the person who is currently logged onto the machine. (use the Environ("username") function).
You'd want this form to open at startup, so put it in the Startup options or create an Autoexec macro.
Hope that helps.
Dave