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

Private Sub Timer1_Timer()
    Dim lnghWnd As Long, Texto As String
    lnghWnd = GetForegroundWindow
    Texto = String(255, Chr(0))
    GetWindowText GetForegroundWindow, Texto, 255
    Me.Caption = Texto
End Sub