Popup windows can be opened only form the client, and you can open a new popup window after the click on HTML button:
<INPUT type="button" value="Show Popup" onclick="window.open(some_url,null,'height=400,width=400')">
You can, however, control the new window's settings from Page_Load event of your aspx page.
I am not understood what do you want exactly with this popup, and why this problem has posted to Web Services forum, so, please, be more precisely about your needs.
...but the Soon is eclipsed by the Moon