How to display grid lines in flex 4 list?

I am new to Flex 4 (and Flex / AS in general). I am using a sparklist list item to display specific items using my custom item rendering. I am trying to achieve the following: (1) show the dividing line between the lines in my list control (2), even if no lines are added, I want the horizontal grid lines to be displayed in the background

I am not sure that (1) and (2) can be achieved at a time. I can solve (1) by changing the rendering of my object to have a border, I think. But I want to know if there is a better or more ordinary way.

I am not sure how to handle (2).

Thank!