I have created a hidden field in my JavaScript and this hidden filed is used to capture the value that users select from the message box. When selection is made from the drop-down box, I am making a call to check if the ID that is selected from the drop down is already in the table, if only the ID is found in the table then I am calling the JavaScript to show the message box. If user Selects Yes show some alert and if user selects No show another alert. Somehow, I am having hard time to make it to work, nothing happens when I make selection from the drop-down. Please help as I have spent days on researching this. thanks
here my code:

 //javascript code

 <script type=text/javascript>

        function Confirm() {

            var confirm_value = document.createElement(INPUT);

            confirm_value.type = hidden;

            confirm_value.name = confirm_value;

            if (confirm(Do you want to delete data?)) {

                confirm_value.value = Yes;

            } else {

                confirm_value.value = No;

            }

            document.forms[0].appendChild(confirm_value);

        }

</script>

//drop down in aspx file

//code behind

  protected void ddl_SelectedIndexChanged(object sender, EventArgs e)

    {



       string ID = ddlName.SelectedValue;



        using (SqlConnection con = new SqlConnection(strConnString))

        {

            using (SqlCommand cmd = new SqlCommand())

            {

                cmd.Connection = con;

                cmd.CommandType = CommandType.Text;

                cmd.CommandText = SELECT count(*) from MyTable WHERE ID =@ID;

                cmd.Parameters.AddWithValue(@ID, ID);

                con.Open();

                int result = (int)cmd.ExecuteScalar();



                if (result >= 1)

                {

                    ScriptManager.RegisterStartupScript(this.Page, Page.GetType(), text, Confirm(), true);

                    string confirmValue = Request.Form[confirm_value];

                    if (confirmValue == Yes)

                {

                    this.Page.ClientScript.RegisterStartupScript(this.GetType(), alert, alert('You clicked YES!'), true);

                }

          else

                {

                    this.Page.ClientScript.RegisterStartupScript(this.GetType(), alert, alert('You clicked NO!'), true);

                }                 



                }

                con.Close();

            }

        }



    }