Private Declare Function GetForegroundWindow Lib "user32" () As Long
Private Declare Function GetWindowText Lib "user32" Alias "GetWindowTextA" ( _
  ByVal hwnd As Long, ByVal lpString As String, ByVal cch As Long) As Long
  Dim Wintext As String
  Dim forewin As Long
 
 
Private Sub GetWindowInfo(handle As Long, p As String)
  p = Space(1024)
On Error Resume Next
  GetWindowText handle, p, 1024
 
  p = Left(p, InStr(1, p, Chr(0)))
End Sub
 
Private Sub Timer1_Timer()
forewin = GetForegroundWindow
GetWindowInfo forewin, Wintext
Label1.Caption = Wintext                 ' Wintext ist die Caption
End Sub

Private Declare Function EnableWindow Lib "user32" (ByVal hwnd As Long, ByVal _
  fEnable As Long) As Long
 
Private Sub BlockWindow()
EnableWindow forewin, false
End sub
 
Private Sub UnblockWindow()
EnableWindow forewin, true
end sub