This is probably more a Javascript problem, but maybe somebody can help me

This is probably more a Javascript problem, but maybe somebody can help me:

I made a php-page (blablabla.php).
The page contains a form with a radiogroup (name=nwstatus) and a
submit-button, the radiogroup has 3 radio buttons (value=1, value=2,
value=3).
When the page is initially loaded no radio button may be checked (the page
is called with variable nwstatus=0: http://.../blablabla.php?nwstatus=0).

On checking a radiobutton, the page must be reloaded, after reloading the
selected radiobutton must be checked.
Depending on which radiobutton is checked, some 'select's may appear.
After making a choice in the select-options, the form must be submitted
through a button.

<input name="nwstatus" type="radio"

onChange="document.location='blablabla.php?nwstatu s='+this.form.nwstatus.val
ue" value="1"
<?php if ( $_GET['nwstatus']=="1"){echo "checked";}?> >In<br>
<input name="nwstatus" type="radio"

onChange="document.location='blablabla.php?nwstatu s='+this.form.nwstatus.val
ue" value="2"
<?php if ( $_GET['nwstatus']=="2"){echo "checked";}?> >New
location<br>
<input name="nwstatus" type="radio"

onChange="document.location='blablabla.php?nwstatu s='+this.form.nwstatus.val
ue" value="3"
<?php if ( $_GET['nwstatus']=="3"){echo "checked";}?> >Defect<br>

<?php if ($_GET['nwstatus']==2) { ?>
<select name="menu1" ><option selected>unnamed1</option></select>
<select name="menu2" ><option selected>unnamed1</option></select>
<?php }?>

<input type="Submit" name="Submit" value="Submit">


Problem:
When I call the page, is initially loaded without a checked radiobutton (as
I wished)
When I select a radio button, nothing happens.
When I select another radio button, the page is reloaded but the value of
the radiogroup is not sent.
(the adress indicates: http://.../blablabla.php?nwstatus=undefined)

I have tried the events onClick, onAfterupdate, onSelect instead of
onChange, but without success.
It seems to be that the onChange-event does not happen on the first
selection, and that the Javascript that gets the radiobutton-value is not
correct.
I am not very good in JavaScript, maybe you are?
Who can give me some advise?