var bkg_outer = null;
var bkg_inner = null;

var bkg_i = 40;

var bkg_outer_left_off = 0;
var bkg_outer_top_off = 0;
var bkg_inner_left_off = -40;
var bkg_inner_top_off = -40;

var bkg_task;

function start_slider(outer_id,inner_id,inner_x,inner_y)
{
	bkg_inner_left_off = -inner_x;
	bkg_inner_top_off = -inner_y;
	
	if (document.getElementById)
		{
		bkg_outer = document.getElementById(outer_id);
		bkg_inner = document.getElementById(inner_id);
		
		if (bkg_outer && bkg_inner)
			bkg_task = window.setInterval("slide_bkg()",150);
		}
}

function slide_bkg( )
{
	if ( bkg_i > 0 )
		{
		bkg_i -= 1;
		bkg_outer.style.backgroundPosition = (bkg_outer_left_off-bkg_i) + "px " + (bkg_outer_top_off-bkg_i) + "px";
		bkg_inner.style.backgroundPosition = (bkg_inner_left_off+bkg_i) + "px " + (bkg_inner_top_off-bkg_i) + "px";
		}
	else
		{
		window.clearInterval(bkg_task);
		}
}