HTML Form post to popup-window

[magix]

Hi,

I launched a modal popup window with code like:
<script language="javascript">
function modalWin() {
if (window.showModalDialog) {
window.showModalDialog("MyPage1.asp","MyPopup",
"dialogWidth:500px;dialogHeight:400px");
} else {
window.open('MyPage1.asp,'MyPopup',
'height=400,width=500,toolbar=no,directories=no,st atus=no,menubar=no,scrollbars=no,resizable=no ,modal=yes');
}
}
</script>

so can see that the popup window name is MyPopup, with MyPage1.asp

In MyPage1.asp, I got FORM statement to post

<form method="POST" action="MyPage2.asp" onsubmit="return
confirmStart()" id="submitform" name="sform" target="_self">

I have tried with Target="_self" or target="MyPopup", but still it
will open another new popup window. Why?

Since I already have MyPopup windows, for any form post, I want it to
be at the same window.
Meaning that the popup window name is STILL be the same MyPopup, with
MyPage2.asp

Can you help ?

Magix