Hiren,
You can access the parent window objects in the child window using the window.opener property. You can place a hidden field in your parent window (say with id - hidText), you set that field in click windows closing (or any event) like -
window.opener.document.getElementById('hidText').value = enteredtext;
you can get the value from hidden field on your submit button click.
for more -
http://www.webreference.com/js/tutorial1/opener.html