Anyone know javascript?

I have a grid(4 x 4) of 16 spacer images and a few text links on the side. Each text link represents a different folder of images. When you rollover each text link, I want a random spacer image (1-16) to display a random image from an array. So for example, the first text link is people-- when you rollover the word people I want a random square to show one of the seven pictures. The you rollout and back over the text link people and a different square shows a different picture out of the same array.

The thing is, i have no idea how to do that.

Can anyone help??