check if one of a group of radio buttons have been checked

I have a problem with my JavaScript validation.

In my JavaScript function i am trying to check if a radio button has been checked
before more code is ran.

My problem only appears when there is more than one adult.

This is my JS code if there are MORE than one adult:



kostenzahler = 0;

for (counter = 0; counter <= form.pass.length; counter++)
{
alert("CONTROL loop = " + counter);
if (document.forms["form"].elements["pass"].checked)
{
radio_choice = true;
kostenzahler = kostenzahler + 1;
}
}


This code works when there is only ONE ADULT:

if (document.forms["form"].elements["pass"].checked)
{
alert("UBERPRUFT!")
radio_choice = true;
}



This is my server-side code (ASP):
(noa = 2 for example)

<% for x = 1 to noa %>
<td id="ADTcell:<%=x%>">
<%
if CInt(x) <= CInt(noa) then
%>
<input type="radio" name="pass" id="adt<%=x%>" onMouseOver="style.cursor='hand'"/>
<%
else
response.Write "&nbsp;"
end if
%>
</td>
<% next %>