I'm trying to limit the amount of checkboxes that someone can choose. I want to be able to compare 2 mortgage payment frequencies. Any two can be chosen of Monthly, Bi-Weekly and Weekly. For some reason I am getting an error.

Can someone please help me?

Here is what I have:

index.htm:

<script type="text/javascript" language="javascript" src="mortgraph.js"></script>

...


	<form>
		Compounding:  
		<select name="comp">
			<option value="2" selected>Semi-annual</option>
			<option value="12">Monthly</option>
		</select><br><br>
		Mortgage Amount: <input type="text" name="amt"><br><br>
		Interest Rate: <input type="text" name="i"><br><br>
		Amortization (years): <input type="text" name="am"><br><br>
		Select to compare (max. 2): 
		<input type="checkbox" name="monthly" checked onclick="alert();"> &nbsp;Monthly&nbsp;&nbsp;&nbsp;
		<input type="checkbox" name="biweekly" checked onclick="max2();"> &nbsp;Bi-Weekly&nbsp;&nbsp;&nbsp;
		<input type="checkbox" name="weekly" onclick="max2()"> &nbsp;Weekly
	</form>

mortgraph.js:

function max2() {
	var numchecked = 0;
	
	var typ = document.getElementByName('weekly');
	alert(typ);
	if(numchecked > 2) { 
		alert("I'm sorry, you can only view one or two frquencies at a time.");
		return false;
	} else {
		return true;
	}
}

HTML:

 <form>
  Compounding:  
  <select name="comp">
   <option value="2" selected>Semi-annual</option>
   <option value="12">Monthly</option>
  </select><br><br>
  Mortgage Amount: <input type="text" name="amt"><br><br>
  Interest Rate: <input type="text" name="i"><br><br>
  Amortization (years): <input type="text" name="am"><br><br>
  Select to compare (max. 2): 
  <input type="checkbox" name="compare_1" value="monthly" checked onclick="boxchk(this,2);"> &nbsp;Monthly&nbsp;&nbsp;&nbsp;
  <input type="checkbox" name="compare_2" value="biweekly" checked onclick="boxchk(this,2);"> &nbsp;Bi-Weekly&nbsp;&nbsp;&nbsp;
  <input type="checkbox" name="compare_3" value="weekly" onclick="boxchk(this,2)"> &nbsp;Weekly
 </form>

Javascript:

function boxchk(obj,max) {
  var box = obj.name.substr(0,obj.name.lastIndexOf('_')+1);
  var cnt=0,i=1;
  while(obj.form[box+i]) {
    cnt += obj.form[box+i].checked;i++;
  }
  if (cnt > max) {obj.checked = false;
    alert('Only choose ' + max + ' '+ box.substr(0,box.length-1) +' checkboxes.\nTo pick this option unselect one of the others.');
  }
}

thanks mgraphic...

It seems as though you keep bailing me out.