Выбрать все, снять все

<SCRIPT LANGUAGE="JavaScript">
<!-- Begin
function checkAll() {
for (var j = 1; j <= 14; j++) {
box = eval("document.checkboxform.C" + j);  
if (box.checked == false) box.checked = true;
  }
}

function uncheckAll() {
for (var j = 1; j <= 14; j++) {
box = eval("document.checkboxform.C" + j);  
if (box.checked == true) box.checked = false;
  }
}

function switchAll() {
for (var j = 1; j <= 14; j++) {
box = eval("document.checkboxform.C" + j);  
box.checked = !box.checked;
  }
}
// End -->
</script>

<center>
<form name=checkboxform>
<input type=checkbox name=C1 checked>C1<br>
<input type=checkbox name=C2 checked>C2<br>
<input type=checkbox name=C3 checked>C3<br>
<input type=checkbox name=C4 checked>C4<br>
<input type=checkbox name=C5 checked>C5<br>
<input type=checkbox name=C6 checked>C6<br>
<input type=checkbox name=C7 checked>C7<br>
<input type=checkbox name=C8 checked>C8<br>
<input type=checkbox name=C9 checked>C9<br>
<input type=checkbox name=C10 checked>C10<br>
<input type=checkbox name=C11 checked>C11<br>
<input type=checkbox name=C12 checked>C12<br>
<input type=checkbox name=C13 checked>C13<br>
<input type=checkbox name=C14 checked>C14<br>
<br>
<input type=button value="Выбрать все" onClick="checkAll()"><br>
<input type=button value="Снять все" onClick="uncheckAll()"><br>
<input type=button value="Выбрать/снять" onClick="switchAll()"><br>
</form>
</center>