asp.net 2.0 script callback problem

I have created a page which is having a tree view control and a grid view.
The treeview lists categories and when i click a category the gridview
populates some data in that category. i have used script callback in Asp.net
2.0 to populate gridview. When i click a treeview link, the callback function
will pass the corresponding category Id to the server and, the gridview is
populated for that CategoryId. The code is as listed below.

using (DataSet dsProcs =
objProcedureList.GetProceduresNotInStoreForCategoryID(
this.LibraryID,
Int32.Parse(CategoryIDFromCategoryTree)))
{
DataView dvProcs =
dsProcs.Tables["TblProcedureList"].DefaultView;
if (dvProcs.Count > 0)
{
gvProcsInCategory.DataSource = dvProcs;
gvProcsInCategory.DataBind();

// Create Html Text Writer
StringWriter sw = new StringWriter();
HtmlTextWriter htw = new HtmlTextWriter(sw);
gvProcsInCategory.RenderControl(htw);
//Return values
return sw.ToString();
}

In the javascript side
function ReceiveServerData(rValue)
{
document.getElementById("MyDiv").innerHTML = rValue;
}
is used to display the server result.

I have added a template column of checkboxes to the gridview control and a
Button to the aspx page next to this.
My intension is to collect the rows, in which the checkbox is checked by the
user.
But when i checked the rows and clicked the button, in the button click
event, it looks like the grid is not binded to any data.The nof rows shows
as zero.
Plese help me to get the desired result..


Thanks in advance.