// 

var cbx = new Array();

function selectionComplete() {
  var sel = 0;
  for (i=0; i<cbx.length; i++) {
     if (cbx[i].checked) sel++;
  }

   return (sel > 7);  
}


function disableOtherCB() {
  for (i=0; i<cbx.length; i++) {
     if (!(cbx[i].checked)) cbx[i].disabled = 'disabled';
  }
}

function enableAllCB() {
  for (i=0; i<cbx.length; i++) {
     if (cbx[i].disabled) cbx[i].removeAttribute('disabled');
  }
}


function setCbListener() {
  frm = document.getElementById('cbx');
  inp = frm.getElementsByTagName('input');
  for (i=0; i<inp.length; i++) {
     if (inp[i].type == 'checkbox') {
       cbx.push(inp[i]);
       setCbOnclick(inp[i]);
     }
  }
}

function setCbOnclick(cb) {
  cb.onclick = function() {
     if (selectionComplete()) {
        disableOtherCB();
     }
     else {
        enableAllCB();
     }

  }
}

window.onload = setCbListener;