Within my control. Ascx a treeview I want to update without the postback to make the whole page.
Full two lists and what apartir selected in the second list box add nodes to a group of treeview

my button
<input id="Button1" type="button" value="button" onclick="return Ejecutar()" /><br />

//Function of javascript
function Ejecutar() {
var message = 'Ejecutar';
var context = 'Map1'; //this variable is for update other control
<%=CallbackBotonEjecutar%>

}

...Treeview1.......

this code is of source

the codeBehind is next...
Public Sub RaiseCallbackEvent(ByVal eventArgument As String) Implements System.Web.UI.ICallbackEventHandler.RaiseCallbackEvent

If eventArgument.Contains("Ejecutar") Then
LLenaxOrganismo(TreeView1.Nodes.Item(1))

End If

End Sub

Public Function GetCallbackResult() As String Implements System.Web.UI.ICallbackEventHandler.GetCallbackResult
Return _callbackArg
End Function

Private Sub LLenaxOrganismo(ByVal nodePadre As EO.Web.TreeNode)
con.ConnectionString = "Data Source=0.0.0.0;persist security info=True;Initial Catalog=database;User ID=user;password=psw"
con.Open()
Try
Dim cmd As SqlCommand = con.CreateCommand
cmd.CommandText = "spOrganismo"
cmd.Parameters.AddWithValue("@Organismo", ddlCriterio.Text) 'this ddlcriterio is a dropdonwlist to choose option text
cmd.CommandType = Data.CommandType.StoredProcedure
Dim da As New SqlDataAdapter(cmd)
Dim ds As New Data.DataSet
da.Fill(ds)

Dim dataViewHijos As Data.DataView
dataViewHijos = New Data.DataView(ds.Tables(0))
TreeView1.DataSource = ds
If TreeView1.Nodes.Item(1).SubGroup.Nodes.Item(0).Text = "Ductos" Then
For Each dataRowCurrent As Data.DataRowView In dataViewHijos
Dim nuevoNodo As New TreeNode
nuevoNodo.Text = dataRowCurrent("Ducto").ToString()
If nodePadre Is Nothing Then
TreeView1.Nodes.Add(nuevoNodo.Text)
Else
TreeView1.Nodes.Item(1).SubGroup.Nodes.Item(0).SubGroup.Nodes.Add (nuevoNodo.Text)
End If
Next dataRowCurrent
End If
Catch sqlEx As SqlException
'MsgBox(sqlEx.Message)
Catch ex As Exception
'MsgBox(ex.Message)
End Try
If con.State = Data.ConnectionState.Open Then
con.Close()
End If
'm_map is a control for a map
m_map.CallbackResults.Add(RefreshControlHtml(TreeView1))
_callbackArg = m_map.CallbackResults.ToString
End Sub

'whit this function refresh my ASP controls correctly
Private Function RefreshControlHtml(ByVal control As Control) As ESRI.ArcGIS.ADF.Web.UI.WebControls.CallbackResult
Dim sw As System.IO.StringWriter = New System.IO.StringWriter()
Dim writer As HtmlTextWriter = New HtmlTextWriter(sw)
control.RenderControl(writer) 'here send error
'Referencia a objeto no establecida como instancia de un objeto.
Dim htmlContent As String = sw.ToString()
sw.Close()
Return New ESRI.ArcGIS.ADF.Web.UI.WebControls.CallbackResult(control, "content", htmlContent)
End Function

thanks for help me!!!!!

Thanks for your answer, now my Treeview execute correctly whit callback