Control Event (Changed) In DataTable - vb.net

Question

Helo:
How to overcome the problem of [RowChanged] event within the [DataTable] in the [DataGridView].
Explanation: You have created a column in the dataTable to find out which rows have been modified, in order to facilitate the knowledge of these rows to update them in the database, but the problem in the event(Row_Changed), can not be explained by more words in the code, see the column of (ISCHANGE) after modifying any row and cover the The Save button you find takes the value True and then False;
Public Class Class1
Public Table As DataTable
Sub New()
Table = New DataTable
Table.Columns.Add("IsChange", System.Type.GetType("System.Boolean"))
Table.Columns.Add("TeacherName", System.Type.GetType("System.String"))
Table.Columns("IsChange").DefaultValue = False
Dim dr As DataRow = Table.Rows.Add
dr("TeacherName") = "X1"
dr = Table.Rows.Add
dr("TeacherName") = "X2"
dr = Table.Rows.Add
dr("TeacherName") = "X3"
dr = Table.Rows.Add
AddHandler Table.RowChanged, New DataRowChangeEventHandler(AddressOf Row_Changed)
End Sub
Sub New(SourceDataTable As DataTable)
'Import DataTable
Table = SourceDataTable
End Sub
Public Sub Save()
GotoChange = False 'disable the event (Row_Changed)
For ALoop As Integer = 0 To Table.Rows.Count - 1
'=======================================
'Here Code Save To DataBase
'
'
'=======================================
Table(ALoop)("IsChange") = False 'RowChanged =False
Next
GotoChange = True 'Enabled the event (Row_Changed)
End Sub
Dim GotoChange As Boolean = True 'This variable is to disable the event (Row_Changed)
Private Sub Row_Changed(ByVal sender As Object, ByVal e As DataRowChangeEventArgs)
If Not GotoChange Then Exit Sub
If e.Action = DataRowAction.Add Or e.Action = DataRowAction.Change Then
If CBool(e.Row("IsChange")) = False Then
MsgBox("IsChange")
e.Row("IsChange") = True 'If [True] this means that the row has been changed
End If
End If
End Sub
End Class
Form Code :
Change Any Row Then Button Save:
Public Class Form1
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Dim A As New Class1
Me.DataGridView1.DataSource = A.Table
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim A As New Class1(Me.DataGridView1.DataSource)
'Change Value Any Row Then Button Save
'Here Problem: Show Column(IsChang) After Save
'The value First (False) Then (True)
A.save()
End Sub
End Class