How to dynamically set the AutoCompleteExtender ContextKey?

<asp:content ID="Content1" ContentPlaceHolderID="plcMainArea" Runat="Server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
        <Services>
            <asp:ServiceReference Path="WebService.asmx" />
        </Services>
    </asp:ScriptManager>
 
<script type = "text/javascript"> 
  function UpdateOfficeID()
  {
  var behavior = $find('ace2');
  var value = '';
 
  value = readCookie('office','&');
  value = value.substring(3,value.length);
  alert('!'+value+'!');
 
 
  if (behavior)
  {
    behavior.populate(value);
  }
}
 
Sys.Application.add_load(function(){UpdateChurchID();});
 
function readCookie(name,delimit)
{
  if (document.cookie == '')
  {
    return false;
  }
  else
  {
    var fC,lC;
    var mcookie = unescape(document.cookie);
    fC = mcookie.indexOf(name);
    var ph = fC + name.length;
    if ((fC != -1) && (mcookie.charAt(ph) == '='))
    {
      fC += name.length + 1;
      lC = mcookie.indexOf(delimit,fC);
      if (lC == -1) lC = mcookie.length;
      return unescape(mcookie.substring(fC,lC));
    }
    else
    {
      return false;
    }
  }
}
 
 
 
 
</script>
 
<asp:TextBox ID="txtPerson2" runat="server" ></asp:TextBox>
                  <cc1:AutoCompleteExtender ID="AutoCompleteExtender2" runat="server"
                    BehaviorID="ace2" 
                    ServicePath="~/WebService.asmx" 
                    ServiceMethod="GetPeopleList" 
                    MinimumPrefixLength="1" 
                    TargetControlID="txtPerson2"
                    CompletionInterval="1000" 
                    CompletionSetCount="20"
                    CompletionListHighlightedItemCssClass="list_hilight"
                    CompletionListItemCssClass="list_item" > 
                </cc1:AutoCompleteExtender>
</asp:content>
 
Below is my modified web service code behind. This doesn't return anything:
 
Imports System
Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web
Imports System.Collections
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Web.Script.Services
 
 
 
<System.Web.Script.Services.ScriptService()> _
<WebService(Namespace:="http://tempuri.org/")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
Public Class WebService
    Inherits System.Web.Services.WebService
 
    <WebMethod()> _
    Public Function GetPeopleList(ByVal contextKey As String) As String()
 
        Dim people As String()
        Dim intCount As Integer = 1
        Dim strPerson As String
 
        people = New String(intCount) {}
        people.SetValue("You selected ofice " + contextKey, 0)
        
        Return people
 
 
    End Function
 
End Class
 
Below is my original web service code behind. This works, only if the contextKey is hard-coded into the autocompleteextender control. If I use the javascript/behaviorid code above with the below code, it doesn't work:
 
Imports System
Imports System.Configuration
Imports System.Data
Imports System.Data.SqlClient
Imports System.Web
Imports System.Collections
Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.Web.Script.Services
 
 
 
<System.Web.Script.Services.ScriptService()> _
<WebService(Namespace:="http://tempuri.org/")> _
<WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
Public Class WebService
    Inherits System.Web.Services.WebService
 
    <WebMethod()> _
    Public Function GetPeopleList(ByVal prefixText As String, ByVal contextKey As String) As String()
 
        Dim connect_string As String = ConfigurationSettings.AppSettings("ConnectionString")
        Dim objConnection As New SqlConnection(connect_string)
        Dim objCommand As New SqlCommand
        Dim da As SqlDataAdapter
        Dim dt As DataTable
        Dim dr As DataRow
        Dim people As String()
        Dim i As Integer = 0
        Dim intCount As Integer
        Dim strPerson As String
 
 
        Dim strSQL As String = "SELECT * from care_people " _
            & "INNER JOIN care_people_organisations ON care_people.ID = care_people_organisations.personID " _
            & "WHERE last_name like @prefixText AND care_people_organisations.officeID = @contextKey"
 
        da = New SqlDataAdapter(strSQL, ConfigurationManager.AppSettings("ConnectionString"))
        da.SelectCommand.Parameters.Add("@prefixText", SqlDbType.VarChar, 50).Value = prefixText + "%"
        da.SelectCommand.Parameters.Add("@contextKey", SqlDbType.Int).Value = contextKey
        dt = New DataTable
        da.Fill(dt)
 
        intCount = dt.Rows.Count - 1
        If intCount < 0 Then intCount = 0
 
        people = New String(intCount) {}
 
        For Each dr In dt.Rows
            strPerson = dr("last_name").ToString & ", " & dr("first_name").ToString
            people.SetValue(strPerson, i)
 
            i = i + 1
        Next
 
        Return people
 
 
    End Function
 
End Class
                                              

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