That's not enough information to write a script. I guess I didn't it clear enough earlier: You must determine whether your combo box is bound to an Outlook property (if so, what?) or is unbound. This is covered on the page I suggested.

I would also suggest that you at least try the very simple scripts that are already on that page. You might surprise yourself with your ability to do the job on your own. You'll certainly be the one maintaining the form and its code, so you ought to develop an understanding of how it works.