Help with Javascript on rollOver

[Mr.]

I have a div in my HTML that that when rolled over reveals an image.

I can't figure out how to place a random image from a set of 5 images to appear in the background of that div when it is rolled over again. Please help me!

[Desmondowq]

There is more than one way of writing this. Hope it helps

HTML
<div id='picture' onmouseover="mouseover()"></div>

JS
function mouseover(){
var rand_Img = Math.floor(Math.random()*5+1);
var img_roll_over = document.getElementById('picture').style.backgroundImage="url(Image_"+rand_Img+".jpg)";

}

[Mr.]

awesome thank you!