call server side function of parent page from popup page in asp.net

Hi
I open a pop up page(child page) by using jquery(jquery.colorbox.js) in asp.net application. now when I click on search button I want to close the pop up page(child page) and refresh the UpdatePanel1 by using search parameters. for above I need to execute server side function in parent page. so please can any one help me how can I call server side function while closing pop up page and I should be able to get search parameter values in server side function.
code to close pop up:
child.aspx:
<script>
function closePopup() {
parent.$.fn.colorbox.close();
return true;
}
</script>
// child.aspx.cs:
protected void Page_Load(object sender, EventArgs e) { btnSearch.Attributes.Add("onClick", "return closePopu ...