an example for the javascript function:

function submitit() {
  w_action=window.open('$self_url','action');
  document.forms['main'].submit();
}
[download]

and inside your form you can put:

<INPUT TYPE=BUTTON value=submit onClick='submitit()'>
[download]

I have taken this from a script I wrote some time ago, it is intended just to provide starting point.

---- kurt