onRollOver Image

Hi,
I am laoading two images from an XML file and using a function I had written on muose over the first image the second image should load and on mouse out the first image should load.
bg_mc2.onRollOver = function(){
bg_mc2.contact_mc.loadMovie(“image1.jpg”));
}
bg_mc2.onRollOut = function(){
bg_mc2.contact_mc.loadMovie(image2.jpg);
}
But there is a delay happening in loading the images. On mouse over it takes some time to load the second image.
Is there any other way to load these images so that it can show smoothly the mouse over effect.
Thanks,
Rajesh.