var interval=setInterval("changeBanner();",3000);
var loopNumber = 2
var numberOfBanners = 3

function changeBanner(){

	var whichFunction = "banner_"+loopNumber +" ();"
	eval(whichFunction);
	if (loopNumber == numberOfBanners){
		loopNumber = 1
	}else{
		loopNumber = loopNumber +1
	}

}

function hidethem(){
	for (i=1;i<=numberOfBanners;i++){
	var hideAllBanners= "document.getElementById(\"banner_" +i+ "\").style.visibility = \'hidden\';";
	eval(hideAllBanners);
	}
}

for (t=1;t<=numberOfBanners;t++){

var rotatebanners="function banner_"+t+"(){hidethem();document.getElementById(\"banner_"+t+"\").style.visibility = \'visible\';}"
eval(rotatebanners);
}