Asp 2.0 popupscreen return

Looking for help, I need to know how to return from a popup screen with
either postback or callback. In my popup screen I have input controls with a
save and cancel button at the end. If they click the save button I store the
data in session variables because I have to wait for the user to click the
finish button on the main screen to create database records. If they click
the cancel button I want to return and continue filling out the main screen
until they click the finish button. Any ideas!!

mainscreen.aspx code:

Protected Sub lnkbtnStatements_Click(ByVal sender As Object, ByVal e As
System.EventArgs) Handles lnkbtnStatements.Click
Dim winName As String
winName = " 'myWinStatement' "

Dim strScript As String = "