Private Sub TextBox1_KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles Tclassroom.KeyPress
If IsNumeric(e.KeyChar) = False AndAlso e.KeyChar <> Chr(8) Then
e.KeyChar = Chr(0)
If MsgBox("รับเฉพาะตัวเลข") Then
End If
End If
End Sub