Onmouseover Work In A Function?

Why doesn't a onmouseover function work in a function?
(It's prob due to my code being wrong more than anything else!)

I've got the following code (snippet):

<!-- Begin
var image0 = new Image(); image0.src = "blank.jpg";
var image1 = new Image(); image1.src = "map.jpg";
// End -->

function swapTheImages()
{
image0.src=&#391;.jpg' image1.src=&#392;.jpg' image2.src=&#392;.jpg'
}

When I do an onmouseover and call the function, it doesn't work.
BUT if I put the code in directly - it works!