<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$1"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$2"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$3"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$4"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$5"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$5"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$4"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$3"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$2"/>
<input id="rptOrder_ctl00_chkID" type="checkbox" name="rptOrder$ctl00$chkID"  value="S$1"/><script>
var ci=0;
var val="";
var ck=document.getElementsByName("rptOrder$ctl00$chkID");
for(var i=0;i<ck.length;i++){
ck[i].onclick=function(i){
if(this.checked){
if(ci==0){
val=this.value;
ci++;
}else{
if(val==this.value){
ci++;
}else{
alert("只能选择相同的");
this.checked=false;
}
}
}else{
ci--;
}
}
}
</script>