ช่วยดูโค้ดให้หน่อยคับท่านผู้รู้ VB.net ขอบคุณล่วงหน้าคับ

Public Class Form1

    Private CurrentApp_hWnd
    Private Declare Function GetAsyncKeyState Lib "user32" (ByVal vKey As Long) As Integer

    Private Declare Function GetWindowText Lib "user32.dll" Alias "GetWindowTextA" (ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long

    Private Declare Function GetWindowTextLength Lib "user32.dll" Alias "GetWindowTextLengthA" (ByVal hwnd As Long) As Long

    Private Declare Function GetForegroundWindow Lib "user32.dll" () As Long

    Function GetCaption(ByVal hwnd As Long)
        Dim hWndTitle As String

hWndTitle = String(GetWindowTextLength(hwnd), 0)
        GetWindowText(hwnd, hWndTitle, (GetWindowTextLength(hwnd) + 1))
        GetCaption = hWndTitle
    End Function
    Private Sub Form_Load()
        If GetForegroundWindow <> CurrentApp_hWnd Then
            CurrentApp_hWnd = GetForegroundWindow
            If GetCaption(GetForegroundWindow) = "" Then  Else  : TextBox1.Text = TextBox1.Text & " [" & GetCaption(GetForegroundWindow) & "] - "

        End If
    End Sub
End Class