Public Declare Function GetWindowRect Lib "user32.dll" (ByVal hwnd As Long, _
      ByRef lpRect As RECT) As Long
    Public Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" ( _
    ByVal lpClassName As String, ByVal lpWindowName As String) As Long
    Public Declare Function PostMessage Lib "user32.dll" Alias "PostMessageA" ( _
    ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam _
    As Long) As Long
    Public Const WM_CLOSE As Long = &H10
    Public Structure RECT
        Public Left As Long
        Public Top As Long
        Public Right As Long
        Public Bottom As Long
    End Structure
    Public Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click
        Dim lngHWND As Long, r As RECT
        lngHWND = Me.Handle
        GetWindowRect(lngHWND, r)   'Hier kommt immer der Fehler
        MsgBox("Left=" & vbTab & r.Left & vbCr & _
        "Top=" & vbTab & r.Top & vbCr & _
        "Height=" & vbTab & r.Bottom - r.Top & vbCr & _
        "Width=" & vbTab & r.Right - r.Left)
    End Sub