Opening a submitted form in a new window

[alec]

I was using the following code to submit order_form:

function DoSubmit()
{
document.order_form.target="_self";
document.order_form.action="confirmation_form.asp";
document.order_form.submit();
}

Then I tried to change this code so that not only order_form would submit,
but confirmation_form would open in a new window with parameters of my choice:

function DoSubmit()
{
window.open("confirmation_form.asp","_blank", "top=0, left=0, resizable=0,
scrollbars=1, width=620,height=700");
document.order_form.target="_blank";
document.order_form.action="confirmation_form.asp";
document.order_form.submit();
}

Unfortunately, in this case I am getting 2 windows, each holds
confirmation_form, one window is normal full screen (I do not need it), the
other is what I wanted.
Question: how should code be changed so that order_form would submit to
confirmation_form and only ONE new window would open with parameters of my
choice?
Thank you.