Add following code in child form
<input type="button" value="Close" onclick="javascript:CloseThis()" />
<script type="text/javascript">
function CloseThis() {
window.parent.closeChild(this);
}
</script>
Add following code in parent form.
<asp:Button ID="btnReload" runat="server" CausesValidation="false" Text="Button"
Style="display: none;" OnClick="btnReload_Click" />
<script type="text/javascript">
function closeChild(box) {
$.fn.colorbox.close();
}
function reloadParent(val) {
var btn = document.getElementById('<%=btnReload.ClientID%>');
document.getElementById('<%=hdstatus.ClientID%>').value = val;
btn.click();
}
</script>