Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim result As MsgBoxResult
result = MsgBox("Tuo Testo", MsgBoxStyle.OKCancel)

If result = MsgBoxResult.OK Then
Button1.Text = "ok"
ElseIf result = MsgBoxResult.No Then
Button1.Text = "no ok"
End If

End Sub