Need to get a Hiddenfield falue?

In my project i am having gridview in that one hidden filed is there.Gridview Source
<asp:GridView ID="gdReport" runat="server" AutoGenerateColumns="False" Height="60%" Width="60%" TabIndex="23" ShowHeader="false">
<Columns>
<asp:BoundField HeaderText="Param Name" DataField="S_PARAM_NAME" />
<asp:BoundField HeaderText="Manadatory" DataField="S_MANDATORY" visible="false" />
<asp:BoundField HeaderText="Data Type" DataField="S_DATATYPE" visible="false"/>
<asp:TemplateField>
<ItemTemplate>
<asp:HiddenField ID="lbldatetype" runat="server" Value='<%# Eval("S_DATATYPE") %>'/>
</ItemTemplate>
</asp:TemplateField>
</asp:Gridview>
This is the script for getting values
document.forms[0].onsubmit=function() {
var refFlag = false;
if(srcButton.indexOf('$imgbtnViewReport')==-1 || srcButton.indexOf('$imgbtnClear')==-1 || srcButton.indexOf('$imgbtnExit')==-1)
{
refFlag=true;
}
return refFlag;
}
var reportTable = document.getElementById('ctl00_ContentPlaceHolder2_gdReport');
if('undefined'!=(''+reportTable) && reportTable!=null)
{
var allTrs = reportTable.getElementsByTagName("tr");
if('undefined'!=(''+allTrs) && allTrs!=null)
{
for(i=0;i<allTrs.length;i++)
{
var rowTds = allTrs[i].getElementsByTagName("td");
if (rowTds[1]!=undefined)
{
if(rowTds[1].innerHTML=="DATE")
{
allInputs = allTrs[i].getElementsByTagName("INPUT");
for(j=0;j<allInputs.length;j++)
{
if(allInputs[j].type=="submit")
{
allInputs[j].setAttribute('rowNum',i);
allInputs[j].onclick=showlov1;
}
}
}
else
{
allInputs = allTrs[i].getElementsByTagName("INPUT");
for(j=0;j<allInputs.length;j++)
{
if(allInputs[j].type=="submit")
{
allInputs[j].setAttribute('rowNum',i);
allInputs[j].onclick=ShowDialog;
}
}
}
}
}
}
}
it shows value like
<input type="hidden" Value=DATE ID="ctl00_ContentPlaceHolder2_gdReport_ctl02_lbldatetype">
inthat I need only the Value filed DATE How I can Get the Date value from using above javascript.
If any body knows the answer ,Please help me