Imports System.Text
Public Class Form1
    Declare Function GetForegroundWindow Lib "user32" () As IntPtr
    Declare Auto Function GetWindowText Lib "user32" (ByVal hwnd As IntPtr, _
      ByVal lpString As StringBuilder, ByVal cch As Int32) As Int32
    Private WithEvents T As New Timer With {.Interval = 300, .Enabled = True}
    Private Lbl As New Label With {.AutoSize = True, .Parent = Me}
 
    Private Sub T_Tick(ByVal sender As Object, ByVal e As System.EventArgs) _
      Handles T.Tick
        Dim sb As New StringBuilder(256)
        GetWindowText(GetForegroundWindow, sb, sb.Capacity)
        Lbl.Text = sb.ToString
    End Sub
End Class