Send Balk Data(Datatable) From Child Window To Parent

Currently in one of my .aspx page i was selecting some information from a child window which is opened from a parent window. I opened the window like
window.open('PartNoLookup.aspx','PartNo','left=150, top=60,width=800,height=600, toolbar=no, status=1,scrollbars=yes,resizable=no,dependent=yes');
Some PartNos with their information was selected by the child "PartNoLookup.aspx" page. Now i have to send the part nos to the parent page to be displayed. My parent page was NewQuote.aspx.
Now the problem arises if it was a small value then i could do it with
window.opener.document.getelementById('parentCtrlId').value='Some Value'
But as it was a bulk datatable i can't send it like that.
I stored the DataTable in Session["PartNo"] from the child page. And placed a hidden field "hidFlag" (not with runat='server'. this should be a html hiddenfield) in the Parent Page (i.e. NewQuote.aspx). And wrote some javascript with the Page.ClientScript.RegisterStartupScript like
Page.ClientScript.RegisterStartupScript(typeof(string), "", "refreshParentAndClose();", true);
And inside childpage (PartNoLookup.aspx) i added the JS function refreshParentAndClose() as
function refreshParentAndClose()
{
window.opener.document.getelementById('parentCtrlId').value='checksession'
window.opener.document.forms[0].submit();
window.close();
}
So this function will set the flag in the parent a also submit the page.
Here as the page is postback by some unconventional way, only the PageLoad,PreRender and some processing cycle events will fire in the parent. So i have to check for the flag inside tha Load() event. So i added the checking code in Page_LoadCode as
if(Request.Form["hidFlag"]!=null)
{
string flag=Request.Form["hidFlag"];
switch(flag)
{
case "checksession":
//Check the session and show inside the page.
break;
}
}

Note:Put the hidden field as Html hidden, not with runat=server coz, if you set it server variable then change by the javascript will no be visible as it will be restored from the viewstate. y JavaScript we are changing the value not the stored value inside Encripted ViewState. Also if you use server Hidden field the clientid may not be same as server id. So setting it from child page will be problemetic (but not impossible).