public event CellValueChangedEventHandler CellValueChanged

Public Event CellValueChanged As CellValueChangedEventHandler

using DevExpress.Spreadsheet;
using DevExpress.XtraSpreadsheet;
using System.Drawing;
using System.Globalization;
using System.Windows.Forms;
// ...

public partial class Form1 : DevExpress.XtraBars.Ribbon.RibbonForm
{
    public Form1()
    {
        InitializeComponent();
        spreadsheetControl1.CellBeginEdit += SpreadsheetControl1_CellBeginEdit;
        spreadsheetControl1.CellEndEdit += SpreadsheetControl1_CellEndEdit;
        spreadsheetControl1.CellValueChanged += SpreadsheetControl1_CellValueChanged;

        IWorkbook workbook = spreadsheetControl1.Document;
        workbook.LoadDocument("Products.xlsx", DocumentFormat.Xlsx);

    }

    private CultureInfo CurrentCulture => spreadsheetControl1.Options.Culture;

    private void SpreadsheetControl1_CellBeginEdit(object sender, SpreadsheetCellCancelEventArgs e)
    {
        // Allow users to edit cells only in the 'Unit Price' and 'Units in Stock' columns.
        if (e.Cell.ColumnIndex < 2 || e.Cell.ColumnIndex > 3 || e.Cell.RowIndex < 1 || e.Cell.RowIndex > 19)
        {
            e.Cancel = true;
            MessageBox.Show("You can edit only the 'Unit Price' and 'Units in Stock' values.", "Warning", MessageBoxButtons.OK);
        }
    }

    private void SpreadsheetControl1_CellEndEdit(object sender, SpreadsheetCellValidatingEventArgs e)
    {
        // Validate a value that a user enters into a cell.
        string editorText = e.EditorText;
        bool validValue = e.Cell.ColumnIndex == 2 ? ValidateUnitPrice(editorText) : ValidateUnitsInStock(editorText);
        if (!validValue)
        {
            e.Cancel = true;
            MessageBox.Show("The value you entered is invalid.", "Warning", MessageBoxButtons.OK);
        }
    }

    private bool ValidateUnitPrice(string text)
    {
        // Validate values in the 'Unit Price' column.
        // Convert the obtained string to a Double value. 
        bool conversionResult = double.TryParse(text, NumberStyles.AllowDecimalPoint, CurrentCulture, out double result);
        return conversionResult && result > 0;
    }

    private bool ValidateUnitsInStock(string text)
    {
        // Validate values in the 'Units in Stock' column.
        // Convert the obtained string to an integer value. 
        return int.TryParse(text, NumberStyles.None, CurrentCulture, out int result);
    }

    private void SpreadsheetControl1_CellValueChanged(object sender, SpreadsheetCellEventArgs e)
    {
        if (e.Cell.ColumnIndex != 3)
            return;
        // Highlight zero values in the 'Units in Stock' column.
        e.Cell.FillColor = (e.Value.NumericValue == 0) ? Color.LightPink : Color.White;
    }
}

Imports DevExpress.Spreadsheet
Imports DevExpress.XtraSpreadsheet
Imports System.Drawing
Imports System.Globalization
Imports System.Windows.Forms
' ...

Partial Public Class Form1
    Inherits DevExpress.XtraBars.Ribbon.RibbonForm
    Public Sub New()
        InitializeComponent()
        AddHandler spreadsheetControl1.CellBeginEdit, AddressOf SpreadsheetControl1_CellBeginEdit
        AddHandler spreadsheetControl1.CellEndEdit, AddressOf SpreadsheetControl1_CellEndEdit
        AddHandler spreadsheetControl1.CellValueChanged, AddressOf SpreadsheetControl1_CellValueChanged

        Dim workbook As IWorkbook = spreadsheetControl1.Document
        workbook.LoadDocument("Products.xlsx", DocumentFormat.Xlsx)
    End Sub

    Private ReadOnly Property CurrentCulture() As CultureInfo
        Get
            Return spreadsheetControl1.Options.Culture
        End Get
    End Property

    Private Sub SpreadsheetControl1_CellBeginEdit(ByVal sender As Object, ByVal e As SpreadsheetCellCancelEventArgs)
        ' Allow users to edit cells only in the 'Unit Price' and 'Units in Stock' columns.
        If e.Cell.ColumnIndex < 2 OrElse e.Cell.ColumnIndex > 3 OrElse e.Cell.RowIndex < 1 OrElse e.Cell.RowIndex > 19 Then
            e.Cancel = True
            MessageBox.Show("You can edit only the 'Unit Price' and 'Units in Stock' values.", "Warning", MessageBoxButtons.OK)
        End If
    End Sub

    Private Sub SpreadsheetControl1_CellEndEdit(ByVal sender As Object, ByVal e As SpreadsheetCellValidatingEventArgs)
        ' Validate a value that a user enters into a cell.
        Dim editorText As String = e.EditorText
        Dim validValue As Boolean = If(e.Cell.ColumnIndex = 2, ValidateUnitPrice(editorText), ValidateUnitsInStock(editorText))
        If Not validValue Then
            e.Cancel = True
            MessageBox.Show("The value you entered is invalid.", "Warning", MessageBoxButtons.OK)
        End If
    End Sub

    Private Function ValidateUnitPrice(ByVal text As String) As Boolean
        ' Validate values in the 'Unit Price' column.
        ' Convert the obtained string to a Double value.
        Dim result As Double
        Dim conversionResult As Boolean = Double.TryParse(text, NumberStyles.AllowDecimalPoint, CurrentCulture, result)
        Return conversionResult AndAlso result > 0
    End Function

    Private Function ValidateUnitsInStock(ByVal text As String) As Boolean
        ' Validate values in the 'Units in Stock' column.
        ' Convert the obtained string to an integer value.
        Dim result As Integer
        Return Integer.TryParse(text, NumberStyles.None, CurrentCulture, result)
    End Function

    Private Sub SpreadsheetControl1_CellValueChanged(ByVal sender As Object, ByVal e As SpreadsheetCellEventArgs)
        If e.Cell.ColumnIndex <> 3 Then
            Return
        End If
        ' Highlight zero values in the 'Units in Stock' column.
        e.Cell.FillColor = If(e.Value.NumericValue = 0, Color.LightPink, Color.White)
    End Sub

End Class

if (control != null)
    control.CellValueChanged -= SpreadsheetControl_CellValueChanged;
control = value;

If _control IsNot Nothing Then
    RemoveHandler _control.CellValueChanged, AddressOf SpreadsheetControl_CellValueChanged
End If