How can I cancel a cell edit from the datagridview dataerror subroutine?

Public Class MyDataTable
	Inherits Data.DataTable
 
#Region "Properties"
	Private mbShouldBeValidated As Boolean = True
	Public Property ShouldBeValidated() As Boolean
		Get
			Return mbShouldBeValidated
		End Get
		Set(ByVal value As Boolean)
			mbShouldBeValidated = value
		End Set
	End Property
 
	Private dvrlRules As DataValidationRuleList
	Public Property RuleList() As DataValidationRuleList
		Get
			If dvrlRules Is Nothing Then dvrlRules = New DataValidationRuleList
			Return dvrlRules
		End Get
		Set(ByVal value As DataValidationRuleList)
			dvrlRules = value
		End Set
	End Property
#End Region
 
	Public Sub AddRule(ByVal rule As DataValidationRule)
		RuleList.Add(rule)
	End Sub
 
	Public Overridable Sub Validate(ByVal dr As DataRow, ByVal changedColumnName As String)
		If ShouldBeValidated Then RuleList.Validate(dr, changedColumnName)
	End Sub
 
	Public Overridable Sub Validate(ByVal dr As DataRow)
		If ShouldBeValidated Then RuleList.Validate(dr)
	End Sub
 
#Region "Event handlers"
	Private Sub ColumnChangedEventHandler _
	(ByVal sender As Object, ByVal e As DataColumnChangeEventArgs) Handles Me.ColumnChanged
		Validate(e.Row, e.Column.ColumnName)
	End Sub
 
	Private Sub RowChangedEventHandler _
	(ByVal sender As Object, ByVal e As DataRowChangeEventArgs) Handles Me.RowChanged
		Validate(e.Row)
	End Sub
 
	Private Sub TableNewRowEventHandler _
	(ByVal sender As Object, ByVal e As System.Data.DataTableNewRowEventArgs) Handles Me.TableNewRow
		Validate(e.Row)
	End Sub
#End Region
End Class
 
Public MustInherit Class ValidationRuleBase
#Region "Properties"
	Private msFieldName As String
	Public Property FieldName() As String
		Get
			Return msFieldName
		End Get
		Set(ByVal value As String)
			msFieldName = value.ToUpper
		End Set
	End Property
 
	Private sMessageText As String
	Public Property MessageText() As String
		Get
			Return sMessageText
		End Get
		Private Set(ByVal value As String)
			sMessageText = value
		End Set
	End Property
#End Region
 
#Region "Constructors"
	Public Sub New(ByVal sFieldName As String, ByVal sMessageText As String)
		Me.FieldName = sFieldName
		Me.MessageText = MessageText()
	End Sub
#End Region
End Class
 
Public Class DataValidationRule
	Inherits ValidationRuleBase
 
	Private mDel As DataRowValidationDelegate
 
	Public Function Validate(ByVal dr As DataRow) As Boolean
		Return mDel.DynamicInvoke(dr)
	End Function
 
	Public Sub New(ByVal fieldName As String, ByVal messageText As String, ByVal del As DataRowValidationDelegate)
		MyBase.New(fieldName, messageText)
		mDel = del
	End Sub
End Class
 
Public Class DataValidationRuleList
	Inherits List(Of DataValidationRule)
 
	Public Function Validate(ByVal dr As DataRow, ByVal changedColumnName As String) As String
		If dr.RowState = DataRowState.Deleted Then Return String.Empty
 
		dr.SetColumnError(changedColumnName, String.Empty)
 
		Dim sCurrentError As String = String.Empty
		For Each rule As DataValidationRule In Me
			If rule.FieldName = changedColumnName AndAlso dr.Table.Columns(rule.FieldName) IsNot Nothing Then
				If Not rule.Validate(dr) Then
					'  Concatenate multiple errors for the same column
					sCurrentError = dr.GetColumnError(rule.FieldName)
					If sCurrentError.Length > 0 Then sCurrentError = sCurrentError & "; "
 
					Dim sCaption As String = dr.Table.Columns(rule.FieldName).Caption
					dr.SetColumnError(rule.FieldName, sCurrentError & rule.MessageText(sCaption))
				End If
			End If
		Next
 
		Return sCurrentError
	End Function
 
	Public Function Validate(ByVal dr As DataRow) As String
		If dr.RowState = DataRowState.Deleted Then Return String.Empty 'OrElse dr.RowState = DataRowState.Detached Then Return String.Empty
 
		dr.ClearErrors()
 
		Dim errorList As New System.Text.StringBuilder(256)
		For Each rule As DataValidationRule In Me
			If dr.Table.Columns(rule.FieldName) IsNot Nothing Then
				If Not rule.Validate(dr) Then
					'  Concatenate multiple errors for the same column
					Dim columnError As String = dr.GetColumnError(rule.FieldName)
					If columnError.Length > 0 Then columnError = columnError & "; "
					Dim sCaption As String = dr.Table.Columns(rule.FieldName).Caption
					Dim thisError As String = rule.MessageText(sCaption)
					errorList.AppendLine(thisError)
					columnError &= thisError
					dr.SetColumnError(rule.FieldName, columnError)
				End If
			End If
		Next
 
		Return errorList.ToString
	End Function
 
	Public Sub AddRule _
	(ByVal sMessageText As String, ByVal sFieldName As String, ByVal drvDel As DataRowValidationDelegate)
		Dim rule As New DataValidationRule(sFieldName, sMessageText, drvDel)
		Me.Add(rule)
	End Sub
End Class
 
Public Delegate Function DataRowValidationDelegate(ByVal drwRow As DataRow) As Boolean

                                              

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