Calling Javascript confirm

Code in body of button click (there is a lot before it, so this is just the section in question.)
 
//fields are different
if (dbemail != txtEmail.Text.ToString())
{
     string script = "<SCRIPT LANGUAGE='JavaScript'> ";
     script += "Confirm()";
     script += "</SCRIPT>";
     Page.RegisterStartupScript("ClientScript", script);
}
//field is the same, so call update to update all other information without worring if this is overwritten. 
else       
{
   Update database.
}
 
 
 
 
On the design view, I have this javascript function.
 
<script language="javascript" type="text/javascript">
// <!CDATA[
    function Confirm()
    {    
        var bSave=confirm("Information is different, do you wish to save changes?");
        if (bSave)
        {
            obj=document.getElementById('HiddenField');
            obj.value="1";
        } 
        else 
        {
            obj=document.getElementById('HiddenField');
            obj.value="0";
        }
        __doPostBack();
    }
 
// ]]>
</script>
 
 
 
 
Now, in the page load I try to access the hidden field value, but it is ALWAYS 0 no matter if I click OK or Cancel.
 
 
if(IsPostBack)
{
     if (HiddenField.Value == "1")
     {
         updateFirmInfo();
         updateAgentInfo();
         HiddenField.Value = "0";
     }
     else
     {
          //need script to alert user that no data was updated.
          HiddenField.Value = "0";
     }
}