это будет легко с onChange ()
<input type="radio" name="radioName" value="1" onchange="radio_changed($(this).val())" /> 1 <br />
<input type="radio" name="radioName" value="2" onchange="radio_changed($(this).val())" /> 2 <br />
<input type="radio" name="radioName" value="3" onchange="radio_changed($(this).val())" /> 3 <br />
<script>
function radio_changed(val){
alert(val);
}
</script>