关于setInterval启动但clearInterval不能停止的问题

function setTimer(){

	var spanId;

	<%

	//startRecord

	//endRecord

	c = startRecord+1;

	while(c<=endRecord+1){

	%>

	spanId = 'num<%=c%>';

	if(document.getElementById(spanId)){

		if('' == $.trim(document.getElementById(spanId).innerHTML)){

			time<%=c%> = setInterval("getRandNum('<%=c%>')",10);

		}

	}

	<%

		c++;

	}

	%>

	//time1 = setInterval("getRandNum(num1)",10);

	document.getElementById("start").disabled = true;

	document.getElementById("end").disabled = false;

}



function ct1(showSpan){////////////////////////////////////////////////////////////////

	var divname = 'num'+showSpan;	

	if(document.getElementById(divname)){

		//alert('1');

		$.ajax({

			type: "POST",

			url: "setAction.jsp",

			data: {ac:'getRndNumAndSetOrder',rndOrder:showSpan},

			beforeSend:function(XMLHttpRequest){

				//alert('before');

         	},

			success: function(msg){

				//alert($.trim(msg));

				if('' != $.trim(msg)){

					clearInterval('time'+showSpan);

					document.getElementById(divname).innerHTML = $.trim(msg); 

				}

			},

			complete:function(XMLHttpRequest,textStatus){

				//alert('complete');

			},

			failure:function (result) {  

	            //alert('Failed');  

	        }

		});

	}

}



function ct(){

	<%

	c = startRecord+1;

	while(c<=endRecord+1){

	%>

	ct1('<%=c%>');

	<%

		c++;

	}

	%>

}

屏幕上数字在滚动，想要用clearInterval停止动作，可是按键后无法停止，需要在刷新后才会停止。目前我已经无计可施了，所以来请教下各位大神。