setting a radio button

anyone know how to set a radio button checked with javascript? I'm confused because they have the same name...
<input type=radio name='exampleRadio' value='1'>
<input type=radio name='exampleRadio' value='2'>
so if I want to set the value 2 radio button to checked based on some other user action how do I do it? this.formName.exampleRadio.checked...
thnx.
Joe

Here is a brief example:

<html>
    <head>
        <script language="JavaScript">
            function selectRadioButton(pRadioButton) {
                
                // this is how to iterate through the radio buttons
                //for (var i = 0; i < document.form1.radioButton.length; i++) {
                //    alert(i);
                //}
                document.form1.radioButton[pRadioButton].checked = true;
            }
        </script>
    </head>
    <body>
        <form name="form1">
            <input type="radio" name="radioButton" value="0"> Radio 0<br>
            <input type="radio" name="radioButton" value="1"> Radio 1<br>
            <input type="radio" name="radioButton" value="2"> Radio 2<br>
            <input type="button" value="Select Radio 1" on-Click="selectRadioButton(0)"><br>
            <input type="button" value="Select Radio 2" on-Click="selectRadioButton(1)"><br>
            <input type="button" value="Select Radio 3" on-Click="selectRadioButton(2)">
        </form>
    </body>
</html>

Note change "on-Click" to "onClick", had to post the code like this