[jQuery] animate background-position??

[jQuery] animate background-position??


Hi,
I've been trying several ways to animate the position of a background
image and I'm stuck.
This is the code I'm using:
$("#header").click(function(){
    var bkgPosX=Math.round(Math.random()*(-500));
    var bkgPosY=Math.round(Math.random()*(-200));
    $("#header").animate({style: 'background-position: bkgPosX
bkgPosY;'},'slow');
    });
Any help is much appreciated!
Steve