public event CellEditorOpenedEventHandler CellEditorOpened

Public Event CellEditorOpened As CellEditorOpenedEventHandler

<dxsps:SpreadsheetControl 
    CommandBarStyle="Ribbon" 
    ShowStatusBar="True" 
    ShowFormulaBar="True" 
    Name="spreadsheetControl1"
    DocumentSource="pack://application:,,,/WpfSpreadsheet;component/Documents/Employees.xlsx"
    CellEditorOpened="OnCellEditorOpened">
</dxsps:SpreadsheetControl>

using System.Text.RegularExpressions;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;

namespace WpfSpreadsheet
{
    public partial class MainWindow : DevExpress.Xpf.Core.ThemedWindow
    {
        public MainWindow()
        {
            InitializeComponent();
        }

        Brush editorBackground;
        // Specify the regular expression to check a phone number.
        Regex phoneNumber = new Regex(@"^\(?([0-9]{3})\)?[-.]?([0-9]{3})[-.]?([0-9]{4})$");

        void OnCellEditorOpened(object sender, DevExpress.Xpf.Spreadsheet.CellEditorOpenedEventArgs e)
        {
            // If a user activates an editor for a cell in the "Phone Number" column,
            // the editor's TextChanged event fires. This example assumes
            // that the target cell contains the default editor
            // (a TextBox control).
            if (spreadsheetControl1.ActiveCell.ColumnIndex == 5 &&
                spreadsheetControl1.ActiveCell.RowIndex > 3)
            { 
                // Access the active cell editor.
                TextBox textEditor = e.Editor as TextBox;
                if (textEditor == null)
                    return;
                this.editorBackground = textEditor.Background;
                textEditor.TextChanged += OnTextChanged;
                textEditor.IsVisibleChanged += OnIsVisibleChanged;
            }
        }

        void OnTextChanged(object sender, TextChangedEventArgs e)
        {
            TextBox textEditor = sender as TextBox;
            // If the entered number matches the specified regular expression,
            // convert this number to the standard phone number format.
            if (phoneNumber.IsMatch(textEditor.Text))
            {
                textEditor.Text = phoneNumber.Replace(textEditor.Text, "($1) $2-$3");
                textEditor.Background = editorBackground;
            }
            else
                // Otherwise, change the editor's background color to pink
                // to indicate that the user input is invalid.
                textEditor.Background = Brushes.LightPink;
        }
        void OnIsVisibleChanged(object sender, DependencyPropertyChangedEventArgs e)
        {
            TextBox textEditor = sender as TextBox;
            if (!textEditor.IsVisible)
            {
                textEditor.TextChanged -= OnTextChanged;
                textEditor.IsVisibleChanged -= OnIsVisibleChanged;
            }
        }
    }
}

Imports System.Text.RegularExpressions
Imports System.Windows
Imports System.Windows.Controls
Imports System.Windows.Media

Public Class MainWindow
    Inherits DevExpress.Xpf.Core.ThemedWindow

    Public Sub New()
        InitializeComponent()
    End Sub

    Private editorBackground As Brush
    ' Specify the regular expression to check a phone number.
    Private phoneNumber As New Regex("^\(?([0-9]{3})\)?[-.]?([0-9]{3})[-.]?([0-9]{4})$")

    Private Sub OnCellEditorOpened(sender As Object, e As DevExpress.Xpf.Spreadsheet.CellEditorOpenedEventArgs)
        ' If a user activates an editor for a cell in the "Phone Number" column,
        ' the editor's TextChanged event fires. This example assumes
        ' that the target cell contains the default editor
        ' (a TextBox control).
        If spreadsheetControl1.ActiveCell.ColumnIndex = 5 AndAlso
            spreadsheetControl1.ActiveCell.RowIndex > 3 Then
            ' Access the active cell editor.
            Dim textEditor As TextBox = TryCast(e.Editor, TextBox)
            If textEditor Is Nothing Then
                Return
            End If
            Me.editorBackground = textEditor.Background
            AddHandler textEditor.TextChanged, AddressOf OnTextChanged
            AddHandler textEditor.IsVisibleChanged, AddressOf OnIsVisibleChanged
        End If
    End Sub

    Private Sub OnTextChanged(sender As Object, e As TextChangedEventArgs)
        Dim textEditor As TextBox = TryCast(sender, TextBox)
        ' If the entered number matches the specified regular expression,
        ' convert this number to the standard phone number format.
        If phoneNumber.IsMatch(textEditor.Text) Then
            textEditor.Text = phoneNumber.Replace(textEditor.Text, "($1) $2-$3")
            textEditor.Background = editorBackground
        Else
            ' Otherwise, the editor's background color to pink
            ' to indicate that the user input is invalid.
            textEditor.Background = Brushes.LightPink
        End If
    End Sub

    Private Sub OnIsVisibleChanged(sender As Object, e As DependencyPropertyChangedEventArgs)
        Dim textEditor As TextBox = TryCast(sender, TextBox)
        If Not textEditor.IsVisible Then
            RemoveHandler textEditor.TextChanged, AddressOf OnTextChanged
            RemoveHandler textEditor.IsVisibleChanged, AddressOf OnIsVisibleChanged
        End If
    End Sub

End Class

void SubscribeToEvents() {
    Spreadsheet.CellEditorOpened += OnSpreadsheet_CellEditorOpened;
    SpellChecker.CheckCompleteFormShowing += OnChecker_CheckCompleteFormShowing;

Private Sub SubscribeToEvents()
    AddHandler Me.Spreadsheet.CellEditorOpened, AddressOf OnSpreadsheet_CellEditorOpened
    AddHandler SpellChecker.CheckCompleteFormShowing, AddressOf OnChecker_CheckCompleteFormShowing