$(function(){  
var imgNum = 5;
var imgSize = 940;
var time = 5000;
var current = 1;
setInterval(function(){
if( current < imgNum ) {
current++;
$("#banner ul").animate({
marginLeft : parseInt($("#banner ul").css("margin-left"))-imgSize+"px"
},"fast");
} else {
$("#banner ul").animate({
marginLeft : parseInt($("#banner ul").css("margin-left"))+(imgSize * (imgNum-1))+"px"
},"fast");
current = 1;
}  
}, time);
});