image swap

image swap

I am building an image gallery with jquery fancybox to show before and after photo-retouching. 
Is it possible to apply a roll over behavior to an image that is being pulled from the href attribute in the anchor tag?

The jquery fancybox uses the following syntax to pull to load images

<div class="grid-element">
    <a rel="example_group" href="editorial/01_editorial_lg_on.jpg">                     // large image
    <img id="grid-shadow" src="editorial/01_editorial_sm_on.jpg" alt=""/></a>      // thumbnail
</div>