This is an example:

 

protected CuteEditor.Editor Editor1;
  protected System.Web.UI.WebControls.Label Label1;

  private void Page_Load(object sender, System.EventArgs e)
  {
   // Put user code to initialize the page here
  }

  #region Web Form Designer generated code
  override protected void OnInit(EventArgs e)
  {
   //
   // CODEGEN: This call is required by the ASP.NET Web Form Designer.
   //
   InitializeComponent();
   base.OnInit(e);
  }
  
  /// <summary>
  /// Required method for Designer support - do not modify
  /// the contents of this method with the code editor.
  /// </summary>
  private void InitializeComponent()
  {   
   this.Editor1.PostBackCommand += new System.Web.UI.WebControls.CommandEventHandler(this.Editor1_PostBackCommand);
   this.Editor1.TextChanged += new System.EventHandler(this.Editor1_TextChanged);
   this.Editor1.Initializing += new System.EventHandler(this.Editor1_Initializing);
   this.Load += new System.EventHandler(this.Page_Load);
  }
  #endregion

  private void Editor1_Initializing(object sender, System.EventArgs e)
  {
   //the controls could only register before the CuteEditor Initialized

   Button hello=new Button();
   hello.Text="Hello";
   hello.Style["vertical-align"]="middle";
   hello.CommandName="Hello";
   hello.Click+=new EventHandler(hello_Click);

   Button world=new Button();
   world.Text="World";
   world.Style["vertical-align"]="middle";
   world.CommandName="World";
   world.Click+=new EventHandler(world_Click);

   Editor1.RegisterCustomButton("hello",hello);
   Editor1.RegisterCustomButton("world",world);
  }

  private void Editor1_PostBackCommand(object sender, System.Web.UI.WebControls.CommandEventArgs e)
  {
   Label1.Text="You just click the button : "+e.CommandName;
  }

  private void hello_Click(object sender, EventArgs e)
  {
   Editor1.Text+="<div style='color:red'>Hello Clicked</div>";
  }

  private void world_Click(object sender, EventArgs e)
  {
   Editor1.Text+="<div style='color:red'>World Clicked</div>";
  }

  private void Editor1_TextChanged(object sender, System.EventArgs e)
  {
  
  }

 

You can find the source code of this example in the download package.