How do I increase # of combo box items?

Greetings,

I have been changing my combo box with styles and am completely unable to find how you can increase the number of items that show up in the box when it is opened. Ideally, I would also like to be able to change the vertical space that is allocated for each item in the list (the height of each list item background, not just the font size), but if there is any way to increase the NUMBER of items that a user can view when the box is open that would be very helpful.

Any suggestions? Cheers.

-i