add to JSHeader:

var f;
var hasErrors;
var errorMsgs;

function CheckCBField(field, msg) {
 var ischecked = false;
 for (i = 0; i < field.length; i ++) {
  if (field[i].checked) {
   ischecked = true; // as long as one is chosen this gets set true
  }
 }
 if (ischecked == false) {
  field.className="error";
  errorMsgs += msg + "\n\r";
  return false;
 }
 field.className="";
 return true;
}



add to onload:

var f = document._doc;



add to submit button or onsubmit:


if(CheckCBField(f.FieldName, "failure message if false")) haserrors = true;

...


// validation components completed - display any errors to user return true
if(hasErrors==true) {
	alert(errorMsgs);
	return false;
} else {
	return true;
}


____________________

another version of this function that can also check a lone checkbox:

// validates a checkbox
function CheckCBField(field, msg) {
	var ischecked = false;
	if (field.length == undefined) {
		// only one checkbox, check field for checked w/o index number
		if (field.checked) {
			ischecked = true; // as long as one is chosen this gets set true
			field.className="";
			return true;
		}
	} else {
		// list of options, check list for value
		for (i = 0; i <= field.length; i ++) {
			if (field[i].checked) {
				ischecked = true; // as long as one is chosen this gets set true
				field.className="";
				return true;
			}
		}
	}
	if (ischecked == false) {
		field.className="error";
		errorMsgs += msg + "\n\r";
		return false;
	}
	field.className="";
	return true;
}