Drop-down Menu Contents

I have a form that I would like to create. My primary concern is 2 drop-down menus. The contents of the second drop down menu depend on the selection of the first drop-down menu.

For example: In the first drop-down menu, I want to select a department, and after a department is selected, I want to be able to select one of that department's employees from the second drop-down menu. Of course the content of the employee menu will depend on which department was selected.

I've been experimenting a little bit with my Access database, but how I design that really depends on suggestions I get here, so let me know what you think.

EDIT: I should also mention that the contents need to be read from the Access database, rather than storing everything in a javascript array. In this way, I can have Human Resources add new departments and employees via a web form so that I don't have to manually edit code every day.