//initial checkCount of zero 
var checkCount=1

//maximum number of allowed checked boxes 
var maxChecks=6
var sub;

function setChecks(obj){ 
//increment/decrement checkCount 
if(obj.checked){ 
checkCount=checkCount+1 
}else{ 
checkCount=checkCount-1 
} 
//if they checked a 6th box, uncheck the box, then decrement checkcount and pop alert 
sub = document.bookS.subject.value;
if ((sub.substring(0,8)) == "Business") {
	if (checkCount > 2){
		obj.checked=false 
		checkCount=checkCount-1 
		alert('For Business Studies you may choose ONLY 2 dates at a time.') 
	}
}
else if (checkCount>maxChecks){ 
	obj.checked=false 
	checkCount=checkCount-1 
	alert('Choose up to '+maxChecks+' checkboxes at a time.') 
} 
}