Code:
<html>
<head>
<title>Test</title>
<script type="text/javascript">
<!--
function radioTest(theForm, amount){
j = 0
for (i=0;i<theForm.elements.length;i++) {
if (theForm.elements[i].type == 'radio' && theForm.elements[i].checked) {
j++
}
}
if(j < amount) {
alert('Please choose every box!');
return false;
}
return true;
}
// -->
</script>
</head>
<body>
<form name="requestform" method="post" onSubmit="return radioTest(this, 2);">
<input type="radio" name="question" value="yes">yes
<input type="radio" name="question" value="no">no
<br>
<input type="radio" name="something" value="yes">yes
<input type="radio" name="something" value="no">no
<input type="submit" name="submit" value="submit">
</form>
</body>
</html>
For the 20 radio-group form, change in "radioTest(this, 2)" the number from 2 to 20.
(I know it's rather cheap way, but it works on every form thrown to it)