How Can I Record The Order In Which Checkboxes Are Clicked?

I have written a series of HTML/PHP pages that allow faculty to add their publications to a database to be displayed on a website running over MySQL. It words pretty good, except for one problem... At the bottom of the form, there are a series of checkboxes listing each of the faculty members as a possible author (which are stored in a table in the database). The problem is that when the authors are written to the database, they are stored in their order of occurance in the authors table, not the order "checked" on the submission form. This is a problem because the primary author of the paper is not being listed first.

If I understand it correctly, when the form is posted, there is an array housing which checkboxes are selected is passed. How can I record the checkboxes into that array in the order they are clicked. Does this make any sense?