Open a popup window after a button click

Split off  from http://forums.asp.net/t/883647.aspx

 Here is my situation:
I have a dropdownlist binded with database:
        <asp:DropDownList ID="VisitDateDropDownList" runat="server"  DataSourceID="SqlDataSource1" DataTextField="Visit_Date" DataValueField="Visit_Date" >
        </asp:DropDownList>
And there is a button (after click, pop up a window which goes to the page that updates the database)
 
My question here is:
1. After the new page is updated, how can the new page be closed and back to the old page?
2. I want to see the updated dropdownlist after we close the new page.

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