public RadForm1()
        {
            InitializeComponent();

            this.radRichTextEditor1.Text = "Once upon a time"; 

            radRichTextEditor1.InputHandler = new MyInputBehavior(radRichTextEditor1.RichTextBoxElement);
        }
        
        public class MyInputBehavior : Telerik.WinForms.RichTextEditor.RichTextEditorInputBehavior
        {
            public MyInputBehavior(RadRichTextBox editor) : base(editor)
            {
            }

            protected override void ProcessBackKey(KeyEventArgs e)
            {
                if (e.Control)
                {
                    DocumentPosition startPosition = this.RichTextBox.Document.CaretPosition; 
                    DocumentPosition endPosition = new DocumentPosition(startPosition);
                    startPosition.MoveToPreviousWordStart(); 
                    this.RichTextBox.Document.Selection.AddSelectionStart(startPosition);
                    this.RichTextBox.Document.Selection.AddSelectionEnd(endPosition);
                }
                base.ProcessBackKey(e);
            }
        }