[Javascript] Checkbox challenge

[Shawn Milo]

Try some modification of this:

In each checkbox:  onclick="threeOnly(this)"

function threeOnly(lastChecked){

   var numChecked = 0;

   for (x=0;x<document.forms[0].elements.length;x++){
      if ((document.forms[0].elements[x].type == 'checkbox') && (document.forms[0].elements[x].value == 'on')){
         numChecked++;
      }
   }

   if (numChecked > 3){
      lastChecked.checked = false;
      alert('Please uncheck another option before choosing this one.  You may select a maxumim of three');
   }
   
}



Note: 

Untested, and I sometimes get confused about how you refer to the status of a
checkbox between ASP and Javascript, so my syntax may be screwy, but here's 
something I think you can work with.

Shawn