<!-- Begin
function chequeador(field) {
  var flagy=true;
  for (i = 0; i < field.length; i++) {
    if(field[i].name == "subjects0") { //2
		   if( field[i].checked == true) { //3
          for (j = i+1; j < i+15; j++) { //4
            if(field[j].checked == true) 
                field[i].checked = false;
          } //4
		      if(field[i].checked == true)
		        for (j = i+1; j < i+15; j++) { //5
              field[j].checked = false;
            } //5
			 } //3
			 else
			 { //3
			    for (j = i+1; j < i+15; j++) {
            if(field[j].checked == true) 
               flagy=false;
					}
			    if(flagy) 
					  field[i].checked = true;
			 } //3
   } //2
  }
}
//  End -->