Imports System.Text
Public Class Form1
    Declare Function WindowFromPoint Lib "user32" (x As Int32, y As Int32) As _
      IntPtr
    Declare Auto Function SendMessage Lib "user32" (hWnd As IntPtr, Msg As _
    Int32, wParam As Int32, lParam As StringBuilder) As Int32
    Dim Lbl As New Label With {.Dock = DockStyle.Top, .Parent = Me}
    Dim WithEvents T As New Timer With {.Interval = 300, .Enabled = True}
 
    Private Sub T_Tick(ByVal sender As Object, e As EventArgs) Handles T.Tick
        Dim sb As New StringBuilder(512)
        SendMessage(WindowFromPoint(Cursor.Position.X, Cursor.Position.Y), 13, _
          sb.Capacity, sb)
        Lbl.Text = sb.ToString
    End Sub
End Class